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A portable spark-chamber range spectrometer and electronic data acquisition system is described for acquiring spectral data on energetic charged particles. The instrument system consists of a uni-directional spark-chamber range telescope with pulse-height analysis of the specific energy loss ( d E d x of a charged particle that passes through a triggering telescope. The range telescope consists of a stack of sealed double-gap spark-discharge modules with absorbers sandwiched between them. A Cherenkov counter discriminates against electrons and muons. Cherenkov and d E d x signals are gated by the coincidence circuit. Data, either telemetered or recorded in situ, include the number of coincidences, a clock signal, system voltage levels, and the d E d x , Cherenkov, and spark-discharge module signals. Power consumption of the self-contained system is about 10 W at an event rate of 20 per second and 17 W at an event rate of 100 per second. The standby power is about 8 W. This instrument system can measure primary protons and alphas at balloon altitudes and secondary protons at lower altitudes. A particular configuration with a geometric factor of about 1 cm2 sr has been assembled for measuring atmospheric proton intensities and spectra in the range from MeV to 300 MeV and at altitudes ranging from the altitude of high-flying aircraft to balloon altitudes near the top of the atmosphere.

A self-contained modular instrument determines the average of the transit times of photons from a scintillation event to the photomultiplier tubes attached to the ends of a long scintillator. The mean-timer circuit described here generates a mean-timing pulse that is a true analog computation of the mean arrival time of the two input pulses. The mean timer circuit performs this computation in approximately 50 ns followed by a dead-time of about 75 ns. The measured timing error in generating the mean-timing signal is less than 1.5% the absolute time difference between the two input trigger pulses for absolute time differences up to 20 ns.

A new adsorption isotherm equation for describing solute adsorption from dilute solutions on structurally heterogeneous solids is applied. This equation is associated with a gamma-type distribution function, which characterizes the structural heterogeneity of a microporous solid. Parameters of this equation permit calculating the mean adsorption potential and the dispersion associated with the adsorption potential distribution. These two quantities characterize the energetic heterogeneity of a nonuniform microporous solid. The measured adsorption isotherms of phenol, p-nitrophenol, and p-chlorophenol from dilute aqueous solutions on two samples of activated carbon are used to examine the above-mentioned equation and to evaluate the adsorption parameters that characterize the structural heterogeneities of these samples.

Inclusive neutron spectra were measured at 0/sup 0/ from Nb-Nb and Au-Au collisions at 800 MeV/nucleon. The spectra in the rest frame of the projectile were decomposed into three Gaussians with standard deviations of 55 +- 4, 114 +- 12, and 259 +- 22 MeV/c for Nb-Nb collisions, and 56 +- 4, 110 +- 10, and 279 +- 15 MeV/c for Au-Au collisions. Physical processes associated with each Gaussian are discussed. The dependence of the parameters of the three Gaussians on the impact parameter indicates that the temperature of the spectators excited by peripheral collisions is lower than that excited by nonperipheral collisions, that projectile neutrons involved in nonperipheral collisions have a broader momentum distribution than those involved in peripheral collisions, and that an observed high-energy tail has its origin primarily in nonperipheral collisions. The high-energy tail is explained well by collective backscattering of neutrons in the target from nucleon clusters in the projectile with a mean cluster size of about 1.3 in both Nb and Au.

We present the ratio of experimental 0/sup 0/ (p,n) cross sections with the measured B(M1) values for transitions in several nuclei. Taking the strong spin-flip transition in /sup 12/C for normalization, we find overall good agreement with shell-model predictions for /sup 24/Mg, /sup 28/Si, and /sup 48/Ca. The values of the ratios vary considerably and are very sensitive to the relative amounts of spin and current contributions to each transition. Experimental ratios are also presented for /sup 16/O and /sup 26/Mg.

The adsorption isotherms of propane andn-butane adsorbed on two polystyrene adsorbents with high and low specific surface areas were measured in the concentration range from 500 ppm to 10 800 ppm in a helium carrier gas at 273, 298, 303, and 313K. The isotherms can be represented by either a Freundlich or a Langmuir-Freundlich type equation. The energetic heterogeneities of the two adsorbents were characterized in terms of the dispersion of the adsorption energy. Also, the isosteric heats were calculated from the dimensionless adsorption capacities.

A polynomial equation is used for analyzing ethane adsorption measurements in the low-concentration region carried out by a dynamic chromatographic method for two microporous activated carbons. For low gas-phase concentrations, this equation reduces to Henry's law. It is shown that this polynomial equation gives a good description of hydrocarbon adsorption on microporous activated carbons.

The adsorption and diffusion of ethane in a chromatographic column packed with activated carbon were investigated for different concentrations and flow-rates. The adsorption isotherm of ethane can be represented by a three-parameter equation. The experimental data and theoretical asymptotic concentration profiles agree at high inlet concentrations and deviate at low inlet concentrations. The longitudinal diffusion coefficients were extracted from fitting the experimental data. Analytic criteria presented here for achieving an asymptotic concentration profile predict that the best result occurs at the flow-rate corresponding to the minimum of the height equivalent to a theoretical plate.

Derived here is an energy distribution function that is associated with the Gaussian distribution of micropore sizes, which was introduced by Dubinin for describing gas adsorption on heterogeneous solids with micropores only. A global energy distribution is defined for solids with both micropores and mesopores, and a method is proposed for extracting contributions to this global function arising from the non-uniform microporous structure of a solid and from the surface heterogeneity of mesopores.

Adsorption isotherms of n -butane and 1,3-butadiene and their mixtures on cross-linked polystyrene at 25°C were measured by the frontal analysis method. Single-component isotherms appear to be of the Freundlich type. A binary Freundlich isotherm is adopted for discussing binary data and a method for calculating binary parameters is presented. Another binary Freundlich isotherm, which fails to agree with our data, was examined also.

The gamma micropore-size distribution generates a four-parameter equation for the overall adsorption isotherm. For structurally-heterogeneous solids with very fine micropores, this equation reduces to a simpler three-parameter isotherm equation that gives a good representation of experimental adsorption isotherms. Model studies reveal that this simplified equation permits evaluation of the parameters that characterize the microporous structure. These model studies show also that the simplified equation may be used for describing adsorption on heterogeneous solids with large micropores if their size-distribution resembles a symmetrical distribution function.

Adsorption isotherms for propane and n-butane on two polystyrene samples of high and low specific surface areas were obtained from measurements of transmission or breakthrough curves. These isotherms were analyzed to extract the parameters that characterize the energetic heterogeneity of polystyrene. The energetic heterogeneity of the sample with low specific surface area reflects only the surface heterogeneity of polystyrene; therefore, this sample was used as a reference system to study the polystyrene sample with a high specific surface area. Analysis of the adsorption isotherm suggests that the sample with a high specific surface area possesses micropores that increase its energetic heterogeneity in comparison to that observed for the sample with low specific surface area.

We measured the energy spectra and yields of neutrons above 1.2 MeV from nuclear capture of negative pions slowing down and stopping in C, N, O, Al, Cu, Ta, and Pb targets. Each neutron spectrum was decomposed into an evaporation portion and a direct portion. The number of direct neutrons per stopped pion is substantially constant for all the targets with a mean value of 1.74\ifmmode\pm\else\textpm\fi{}0.28, whereas the yield of evaporation neutrons increases by an order of magnitude from about 0.7 for carbon to about 7 for lead. The total kinetic energy carried away by the neutrons is substantially constant also for all the targets with a mean value of 76.7\ifmmode\pm\else\textpm\fi{}2.0 MeV. The kinetic energy carried away by evaporation neutrons increases with mass number with an associated decrease in the kinetic energy carried away by direct neutrons. We obtained the nuclear temperature (in MeV) of the first residual nucleus formed in the evaporation process for each target: Pb (1.4), Ta (1.4), Cu (1.9), A1 (2.3), O (2.2), N (2.2), and C (2.1). The spectrum from a light target displays a shoulder in the region around 60 MeV which is consistent with a two-nucleon absorption mechanism. The direct neutron spectra are characterized by a rising yield as the neutron energy decreases in the region from 30 MeV down to about 10 MeV. The data are compared with previous measurements and with the predictions of intranuclear cascade and preequilibrium calculations.NUCLEAR REACTIONS C, N, O, Al, Cu, Ta, Pb (${\ensuremath{\pi}}^{\ensuremath{-}}$,$\mathrm{xn}$), ${E}_{{\ensuremath{\pi}}^{\ensuremath{-}}}\ensuremath{\approx}0$ MeV. Measured differential energy spectra and yields. Deduced nuclear temperature. Compared results to intranuclear cascade and preequilibrium model calculations.

Design criteria and performance characteristics are described for large-volume (13.1 1 to 118 1) mean-timed plastic-scintillator detectors for neutrons from ≈2 MeV to 2 GeV. Detectors were constructed in six sizes (all 0.102 m thick) from 0.126 m × 1.016 m × 0.102 m to 0.762 m × 1.524 m × 0.102 m. Overall energy resolutions of 230 keV for 80 MeV neutrons, 320 keV for 133 MeV neutrons, and 440 keV for 157 MeV neutrons were achieved in time-of-flight experiments with flight paths of 76, 68, and 91 m, respectively. The detectors have pulse-height responses uniform to ±5% except close to the ends, position resolutions less than 5 cm, and intrinsic time dispersions less than 400 ps. Typical neutron detection efficiencies are 20% for 20 MeV neutrons at a pulse-height threshold of 2 MeV equivalent-electron energy (MeV ee) and 3.5% for 200 MeV neutrons at a pulse-height threshold of 50 MeV ee.

The wide-angle spectra of the 134-MeV (p,n) reaction on /sup 48/Ca, /sup 54/Fe, /sup 88/Sr, and /sup 208/Pb are each dominated by the excitation of a single state at low excitation energy. These excitations correspond to the ''0h..omega..'' stretched states and are seen to be fragmented much less than ''1h..omega..'' stretched states in medium- and heavy-mass nuclei. The normalization factors required for comparison with distorted-wave impulse-approximation calculations are >0.50 and indicate that these are the purest particle-hole states known in these nuclei.

We measured the breakthrough curves for rectangular pulses of methane, ethane, and acetylene at low concentrations adsorbed on crosslinked polystyrene at 0, 25, and 30°C. The method of moments was utilized to evaluate the diffusion coefficients of the three gases based on a homogeneous-solid diffusion model.

We studied the 28 Si(p, n) reaction with both unpolarized and polarized protons at a nominal energy of 135 MeV, extracted the angular distributions of the differential cross section and the analyzing power for the 6 − , T = 1 state at an excitation energy of 4.95 MeV in 28 P, and compared our results with similar data published for the analog ( p , p ′) reaction to the 6 − , T = 1 state at an excitation energy of 14.35 MeV in 28 Si. These comparisons are consistent with charge independence. The measurements are described well by distorted-wave-impulse-approximation calculations with form factors and spectroscopic amplitudes determined from electron scattering.

Differential cross sections were measured for the /sup 11/B(d,n)/sup 12/C reaction at 79 MeV. Three different adiabatic model calculations as well as conventional distorted-wave Born approximation calculations were performed for transitions to the 0.0, 4.44, 9.64, 12.71, and 15.11 MeV states in /sup 12/C. One of the adiabatic optical model parameter sets gave consistently better agreement than the rest with the experimental data. The spectroscopic factors obtained for the above states were compared with theory and with previous measurements.

Etudes de l'interference d'adsorption de quelques melanges binaires ou d'un melange ternaire d'adsorbats gazeux (CO 2 , ethane, ethylene, benzene, toluene, etc.) dans un gaz entraineur traversant une couche d'adsorbant (charbon actif), a 25°C. Cette interference se manifeste par une reduction de la capacite d'adsorption de chaque composant du melange

We compare the “Lithium Activation” (LiA) method and the “Isospin Clebsch-Gordan Ratio” (ICGR) method for determining detection efficiencies of neutrons between 100 and 160 MeV. Each method was used to determine the efficiency by relating a measured neutron yield to a cross section measured in another way: γ-ray activation cross sections for LiA; (p, p′) cross sections from experiments at the Indiana University Cyclotron Facility for ICGR. Efficiencies determined by the two methods disagree substantially. Efficiencies calculated with the Monte Carlo code of Cecil et al. agree with the ICGR results. We conclude that the Lithium Activation method is inconsistent at these energies.

We measured the transmission curves of binary gas mixtures of esthane and propane (and also of each gas alone) flowing through an adsorber bed at 25°C packed with (Columbia 4LXC 12/28) activated carbon. The adsorption isotherms for pure ethane and propane are described well by a modified Langmuir isotherm known as the Chakravarti-Dhar isotherm. Ethane in the binary mixtures exhibits smaller adsorption capacities than that of pure ethane; however, the presence of ethane does not significantly reduce the adsorption capacity of propane in the mixtures. The ideal adsorbed solution theory (IAST) of Myers and Prausnitz and the semiempirical method of Cook and Basmadjian (C-B) are applied to predict adsorption equilibrium properties of the binary mixtures from the known pure gas isotherms. The pure ethane isotherm data at pressures higher than 10 mmHg are obtained from a correlation formula. Good agreement between the predicted results from the IAST and C-B methods and the experimental results indicates...

The time-dependent concentration of a radioactive gas at the outlet of an adsorber bed for a step change in the input concentration is analyzed by the method of moments. This moment analysis yields analytical expressions for calculating the kinetic parameters of a gas adsorbed on a porous solid in terms of observables from a time-dependent transmission curve. Transmission is the ratio of the adsorbate outlet concentration to that at the inlet. The three non-equilibrium parameters are the longitudinal diffusion coefficient, the solid-phase diffusion coefficient, and the interfacial mass-transfer coefficient. Three quantities that can be extracted in principle from an experimental transmission curve are the equilibrium transmission, the average residence (or propagation) time, and the first-moment relative to the propagation time. The propagation time for a radioactive gas is given by the time integral of one minus the transmission (expressed as a fraction of the steady-state transmission). The ste...

This paper presents a theoretical description of gas adsorption on microporous solids withGaussian micropore-size distributions. This description comprises equations for the overall adsorption isotherm, the adsorption potential distribution, the differential molar enthalpy, and the differential molar entropy of adsorption. The truncatedGaussian micropore-size distribution is assumed to represent the structural heterogeneity of the micropores, whereas the adsorption potential distribution is used to characterize the energetic heterogeneity of these micropores.

We measured neutron time-of-flight spectra from 90 MeV protons and 140 MeV alpha particles bombarding thin targets of Al, Ni, Zr, and Bi at laboratory angles between 20\ifmmode^\circ\else\textdegree\fi{} and 135\ifmmode^\circ\else\textdegree\fi{}. The lowenergy (5 to 45 MeV) portions of the spectra were measured with 5 cm diameter by 5 cm deep NE-213 counters at 1 m flight paths with n-$\ensuremath{\gamma}$ pulse-shape discrimination. The high-energy (35 to 150 MeV) portions of the spectra were measured with 12.7 cm diameter by 10.2 cm deep NE-102 counters at flight paths of 2.0 to 5.0 m. The proton-induced measured neutron spectra reveal three distinct energy regions: a low-energy evaporation region, a high-energy region dominated by the quasifree scattering process, and an intermediate-energy region dominated by multistep, preequilibrium processes. In the latter two regions, the spectra show strong angular dependence. The alpha-particle induced neutron spectra show these same distinct energy regions plus an exponential falloff above the beam energy per nucleon. The neutron spectra are compared with earlier proton spectra produced also by 90 MeV protons and 140 MeV alpha particles. It is observed that the high-energy portions of the forward-angle neutron and proton cross sections are in ratios consistent with the idea that single nucleon-nucleon scattering dominates. For the heavy-mass targets, the low-energy evaporation regions show neutron yields larger than proton yields. The proton-to-neutron ratios observed in the high-energy continua are interpreted with a quasifree calculation fitted simultaneously to the proton and the neutron spectra. Preequilibrium calculations with the exciton model and the hybrid model reproduce the shape of the experimental angle-integrated energy spectra down to lower energies than the quasifree calculations. The exciton model calculations underestimate the magnitudes of the cross sections, while the hybrid model provides better absolute agreement. One of the preequilibrium calculations uses the method of Mantzouranis and Weidenm\"uller to predict angular distributions; we find that the predicted angular distributions overestimate the neutron yields at forward angles. The intranuclear-cascade model predicts proton-to-neutron ratios much smaller than experimentally observed in the high-energy forward-angle continua.NUCLEAR REACTIONS $^{27}\mathrm{Al}$, $^{58}\mathrm{Ni}$, $^{90}\mathrm{Zr}$, $^{209}\mathrm{Bi}$(p,n), ($\ensuremath{\alpha}$, n), ${E}_{\mathrm{p}}=90$ MeV; ${E}_{\ensuremath{\alpha}}=140$ MeV; ${\ensuremath{\theta}}_{L}=20\ifmmode^\circ\else\textdegree\fi{}\ensuremath{-}135\ifmmode^\circ\else\textdegree\fi{}$; measured $\frac{{d}^{2}\ensuremath{\sigma}}{d\ensuremath{\Omega}\mathrm{dE}}$; compared with available experimental proton spectra and with theoretical calculations including PWIA quasifree scattering, preequilibrium exciton, geometry-dependent hybrid, and intranuclear-cascade models.

This paper shows that the exponential adsorption isotherm, which was proposed originally for describing gas adsorption on solids with large pores, is also useful for studying adsorption on heterogeneous microporous solids. For microporous solids, this isotherm generates simple equations for the adsorption potential distribution, the differential enthalpy of adsorption, and the differential entropy of adsorption. The utility of these equations for calculating the above-mentioned thermodynamic functions is illustrated for benzene adsorption isotherms on two different activated carbons.

We measured neutron angular and energy distributions from 710-MeV alphas stopping in targets of water, carbon, steel, and lead for neutron energies from 3 MeV to above 300 MeV. We also measured neutron spectra from 640-MeV alphas stopping in lead. These spectra are similar to the 710-MeV spectra but are reduced in magnitude by about 20 percent. The angular distributions are forward peaked and have a broad bump at about 120 MeV in the 0- and 6-degree spectra. The 710-MeV integrated yields above 10 MeV are about 0.5 neutron per incident alpha, independent of the target. The measured spectra from the water target are consistent with the calculations of an intranuclear cascade model at the forward angles, but are larger than the calculations at the backward angles.NUCLEAR REACTIONS ${\mathrm{H}}_{2}$O, C, steel, Pb($\ensuremath{\alpha}$,$\mathrm{xn}$), $E=710$ MeV; Pb($\ensuremath{\alpha}$,$\mathrm{xn}$), $E=640$ MeV. Measured unidirectional spectra and yields from thick targets. Deduced total integrated neutron yields above 10 MeV. Compared spectra with intranuclear-cascade model.

Multiplicity-selected angular distributions of low-energy neutrons from collisions of 390 MeV/nucleon Ne+Pb are peaked forward, in contrast to relatively flat distributions of protons from Ne+U. A model that includes both Coulomb repulsion and composite-fragment formation accounts for the neutron and proton distributions, and the dependence on nucleon energy of the n/p ratio of inclusive cross sections. This comparison casts doubt on the interpretation of the suppression of forward proton emission as a signal of collective flow.

We measured neutron energy spectra and extracted angular distributions for eleven separate transitions for the /sup 16/O(p,n)/sup 16/F reaction at 99.1 and 135.2 MeV. Several new spin and parity assignments are obtained for states in /sup 16/F by comparison of the excitation energy spectra with known analog states in /sup 16/O and with a shell-model prediction and by analysis of the neutron angular distributions. The most strongly-excited are two 2/sup -/ states at E/sub x/ = 0.40 +- 0.05 and 7.6 +- 0.1 MeV, a 4/sup -/ states at 6.37 +- 0.05 MeV, and two broad 1/sup -/ states at 9.4 +- 0.1 and 11.5 +- 0.1 MeV. These states are analogs of known 2/sup -/ (M2) states, a 4/sup -/ ''stretched'' state, and 1/sup -/ (E1) strength, respectively, in /sup 16/O. Three weakly-excited 1/sup +/ states are observed at E/sub x/ = 3.75 +- 0.05, 4.65 +- 0.05, and 6.23 +- 0.05 MeV. These states are analogs of known 1/sup +/ (M1) states in /sup 16/O and directly indicate correlations in the ground state of /sup 16/O. A weakly excited 4/sup -/ state is seen at 5.93 +- 0.05 MeV in good agreement with a 4/sup -/ state observedmore » in /sup 16/O (e,e') measurements. All of the most strongly excited states align (to within +- 200 keV) with known T = 1 analog states in /sup 16/O for a common net displacement energy of 12.6 MeV. The (p,n) reaction at medium energies is shown to be an important spectroscopic tool.« less

A device is described that compensates variations at the target in the time of arrival of the external cyclotron beam relative to a fixed phase on a radio-frequency signal from the cyclotron. The rf timing compensator permits achieving long-term stability in time resolution for neutron time-of-light measurements at the Indiana University Cyclotron Facility.

We used a dynamic method to measure the adsorption isotherms for the gases ethane, propane, and n -butane on polystyrene at 273, 298, and 303 K. Concentrations were in the range from 500 to 10,000 ppm in a helium carrier. The isotherms can be represented by either Freundlich or Chakravarti-Dhar types. The exponent in the Freundlich isotherm increases with temperature for all three gases. The coefficient in the Freundlich isotherm increases with temperature for propane and n -butane, but decreases with increasing temperature for ethane. The isosteric heats of adsorption show a strong dependence on surface coverage. The isosteric heats were extracted in three ways: (1) from the calculated isosteres, (2) from the adsorption capacities, and (3) from the adsorption potential. The first two methods agree at all measured concentrations. Values derived from the adsorption potentials at 298 K show more variation. The characteristic curves at the three temperatures are superimposable as a single curve for each gas, but polystyrene does not show a single characteristic curve for all three gases.

Time-dependent transmission or “breakthrough” curves of methane in helium flowing through an activated carbon adsorber bed were measured for methane concentrations between 34 and 105 ppm, and for mixture flow rates between 0.69 and 6.64 cm/s. The transmission is the ratio of the outlet concentration to the inlet concentration. The experimental transmission curves for a step-function increase in the methane concentration are compared with the predictions from a model which assumes a linear adsorption isotherm and equilibrium between the gas and solid phases. These two basic assumptions are discussed in detail. The data show that the two assumptions hold within the concentration and flow rate regions of this study. Effective diffusion coefficients of methane were calculated from the transmission data and found to increase with increasing flow rates.

The excitation-energy distribution of transition strength to 1/sup +/ states excited via the /sup 26/Mg(p,n)/sup 26/Al reaction at 134.4 MeV was measured for excitation energies up to 25 MeV. The structures observed in the neutron spectra with ..delta..L = 0 angular distributions were identified as 1/sup +/ states, except for the isobaric analog transition. The total 1/sup +/ strength in this reaction was extracted by normalizing the intensity of the four lowest 1/sup +/ states to the strength measured for the analogous beta decays to these states. A detailed comparison of the experimental results with known analogous transitions and with a large-basis shell-model calculation leads to the conclusion that strengths to states of isospin T = 0, 1, and 2 were observed in this reaction. The apportionment of the observed strength among the three isospin values is compared with the shell-model prediction. The total strength observed to all states below an excitation energy of 15 MeV is 57 percent of the total strength predicted by the shell-model calculation with the assumption of the ''free-nucleon'' normalization of the Gamow-Teller beta decay operator.

The response of NE-228A, NE-228, NE-224, and NE-102 scintillators to protons from 2.43 to 19.55 MeV has been measured relative to electrons. The NE-228A scintillator has the same high hydrogen content (CH 2.11 ) as NE-228; but it has a 30% higher light output. Proton recoils in this energy range were obtained by elastically scattering (20.76±0.13) and (26.08±0.06) MeV neutrons from protons in the scintillators through angles of 20°, 30°, 45°, and 60°. The neutrons were obtained from the T(d, n)α reaction. The measured response (in units of electron energy) for protons above 5 MeV in NE- 102 is about 8% higher than that assumed in popular computer programs for calculating the neutron detection efficiency of plastic scintillators. The response of NE-228A is equivalent to that of NE-228. The response of NE-224 differs from that of either NE-102 or NE-228.

Une equation generale pour l'adsorption de gaz sur des solides microporeux est proposee. Cette equation associee a l'equation de Langmuir permet de formuler une description sur l'adsorption dans des micropores non uniformes. Application du modele a l'adsorption de benzene sur differents charbons actifs

Several improvements have been made to the Monte-Carlo neutron detector efficiency code of Stanton to provide improved agreement with several different detector efficiency measurements.The impovements include a re-adjustment of the inelastic cross sections for neutron-induced reactions on carbon, adoption of new light-response functions, use of relativistic kinematics, and exact determination of light deposited by escaping charged particles. The improved calculations agree with measured efficiences for both plastic and liquid hydrocarbon scintillators for neutron energies from 1 MeV to about 300 MeV and for detector thresholds from about 0.1 MeV to 22 MeV equivalent-electron energies; in most cases the agreement is good to within a few percent.

The reaction {sup 3}He({pi}{sup +},{ital pp}){ital p} was measured at {ital T}{sub {pi}}=350 and 500 MeV in a kinematically complete experiment. Separate contributions from two-body and three-body pion absorption are clearly seen in recoil momentum distributions. The two-body angular distributions closely follow the shape of the free {pi}{ital d}{r arrow}{ital pp} cross section, although the number of deuterons estimated from the two-body yield is larger than the value 1.5 expected from isospin coupling and observed previously at lower energies. Comparison with a simple impulse approximation model suggests some of the enhancement may arise from binding of the quasideuteron, although absorption on {ital T}=1 ({ital pn}) pairs and the higher density of {sup 3}He may also be a factor. The strength of the three-body component falls off with bombarding energy with roughly the same slope as for the two-body component, and accounts for {approx}45% of the total absorption cross section, a larger fraction than reported previously below the (3,3) resonance. The three-body matrix element {vert bar}{ital M}{sub 3}{vert bar}{sup 2} displays an angular dependence at both energies which is suggestive of initial-state interactions. No evidence of final-state interactions is seen.

Spin-flip probabilities for 48Ca( p n )48Sc reveal that at 0° the apparent continuum under and adjacent to the Gamow-Teller giant resonance is also primarily 1+ strength. A comparison of 40Ca[ p n )40Sc and 48Ca( p n )48Sc shows no discernable signature of Gamow-Teller strength in the region −30 > Q(MeV) >−45. The spin-flip component of the dipole resonance for 40Ca is broader than the non-spin-flip component.

Description d'une methode pour determiner la microporosite des materiaux poreux, basee sur les mesures d'isothermes d'adsorption

Neutron spectra from the reaction $^{48}\mathrm{Ca}$($p$,$n$) $^{48}\mathrm{Sc}$ at 160 MeV reveal a prominent narrow peak at ${E}_{x}=16.8$ MeV. This state is interpreted as a spin-flip isovector giant resonance; it carries a significant fraction of the ${T}_{g}$ ($T=4$) Gamow-Teller strength. The observed position of this resonance agrees with both a recent shell-model prediction and with the position expected from systematics for the analog of the giant $M1$ resonance in $^{48}\mathrm{Ca}$.

A correlation formula based on the separation factor is proposed for the mixture concentration in the adsorbed phase of an ideal binary solution in gas-solid adsorption. This formula is shown to apply to two binary systems (viz., 1,3-butadiene and n-butane on cross-linked polystyrene at 25°C, and acetylene and ethane on activated carbon at 25°C) with similar molecular and thermodynamic properties in the two components for each system. Comparison between the calculated and experimental values of the separation factor showed that the assumption of an ideal mixture is justified for each of these two binary systems. Mixture isotherms for the two ideal binary systems are calculated by the proposed correlation formula from the corresponding single-component isotherms. Good agreement between the calculated and experimental mixture isotherm data confirms that a binary system of two components with similar molecular properties (viz., molecular weight, normal boiling point, vapor pressure, number of carbon...

Etude theorique sur la determination du potentiel d'adsorption en fonction de la structure des mesopores et des micropores. Application a la physisorption du benzene sur le charbon actif

Gamow-Teller transition probabilities are extracted for eight nuclei with masses between $A=13 \mathrm{and} 39$ from medium-energy ($p, n$) reactions via the distorted-wave impulse approximation, and compared with experimental $\ensuremath{\beta}$-decay and with free-nucleon transition probabilities. These comparisons indicate strongly that the renormalization of the Gamow-Teller operator needed for ($p, n$) reactions on finite nuclei is different from that needed for $\ensuremath{\beta}$ decay.

An analytical expression is obtained for the equilibrium relationship between the enrichment factor of the product stream and the ratio of the pressure in the feed stream to that in the product stream for a pressure-swing-adsorption system with a Freundlich isotherm. The enrichment factor is the ratio of the mole fraction of the adsorbate in the product gas stream to that in the feed gas stream. The enrichment factor increases with increasing pressure ratio in a manner similar to that for a system with a linear isotherm. The nonlinearity of the Freundlich isotherm does not result in a significant reduction in the enrichment factor.

We measured the analyzing power for the /sup 16/O(p,n)/sup 16/F (4/sup -/, 6.37 MeV) reaction at 134.0 MeV and the differential cross section for the same reaction at 135.2 MeV. The shape of the cross section for the transition to this unnatural parity stretched state is described well by a distorted-wave impulse-approximation calculation using a (..pi..d/sub 5/2/, ..nu..p/sub 3/2//sup ts-1/)/sub 4//sub -/ configuration and the effective interaction derived by Love and Franey from nucleon-nucleon phase shifts. The analyzing power from this calculation reproduces all of the qualitative features of the data and supports the use of the impulse approximation as an excellent starting point for describing the reaction mechanism. Quantitative agreement between the experimental and theoretical analyzing power can be improved by eliminating the imaginary tensor term of this interaction and taking the real part to be that derived by Love from the Sussex matrix elements. The sensitivity of the calculations to the choice of optical potentials and the importance of spin-orbit distortion is explored.

A model is presented for a linear chromatographic reactor with a first-order reaction and three non-equilibrium processes. The following three conclusions are derived based on the Laplace transform of the reactant concentration: (1) the input-output ratio of the reactant is a function of longitudinal diffusion and interfacial diffusion in addition to the reaction rate constant; (2) moment analysis indicates that six parameters pertinent to the linear chromatographic reactor can be determined from the area ratio (or zeroth moment), and the second-order central moment as a function of flow-rate; (3) an approximation to describe the solid-phase concentration by a first-order ordinary differential equation needs a rate coefficient which depends on other parameters of the system besides the solid-phase diffusion coefficient.

Adsorption methods for characterizing the microporosity of activated carbons are discussed critically. Three methods—the αs-method and those based on the Dubinin-Radushkevich and Jaroniec-Choma isotherm equations—are compared with respect to the parameters that characterize the microporous structure of a solid. It is shown that the isotherm equations that account for the structural heterogeneity of activated carbons give values of the micropore volume similar to that obtained by the αs-method.

Excitation-energy distributions of transition strength to ${1}^{+}$ states excited via the (p,n) reaction at 134.4 MeV on targets of $^{76}\mathrm{Ge}$, $^{82}\mathrm{Se}$, $^{128}\mathrm{Te}$, and $^{130}\mathrm{Te}$ were measured for excitation energies up to 25 MeV. Structures observed in the neutron spectra with forward-peaked (\ensuremath{\Delta}L=0) angular distributions were identified as ${1}^{+}$ states, except for the isobaric analog transitions. The total ${1}^{+}$ strength in these reactions was extracted by normalizing the intensity in the ${1}^{+}$ peaks to the Fermi transition strength observed in the isobaric analog state. The Gamow-Teller strength observed in ${1}^{+}$ peaks above a fitted polynomial background is typically 55% of the sum rule obtained by assuming that the strength of ${\ensuremath{\beta}}^{+}$ transitions is negligible. The portion of this strength found at excitation energies less than that of the Gamow-Teller giant resonance varied from 15% for $^{128}\mathrm{Te}$ to 38% for $^{76}\mathrm{Ge}$. Experimental results are compared with predictions of a shell model that includes a pairing force and a long-range Gamow-Teller force in both parent and daughter nuclei. A comparison of the strength functions of the tellurium isotopes is made; this comparison is relevant in determining whether double-beta decay without neutrino emission (0\ensuremath{\nu} decay) is observed in these isotopes.