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The β--decay of 147Cs to 147Ba has been studied by means of γ- and X-ray spectroscopy. A new level scheme of 147Ba is significantly modified and extended in comparison to the one previously reported. The Advanced Time-Delayed βγγ(t) method has been applied to measure half-lives of the 46.2 and 85.4 keV levels in 147Ba yielding T 1/2 of 510(80) ps and 370(100) ps, respectively. The lifetime results combined with the deduced internal conversion coefficients allowed to assign M1 multipolarity to three γ transitions. The B(M1) values obtained for the 39.2, 46.2 and 85.4 keV transitions range from 0.017 to 0.043 W.u. and represent typical B(M1) strength in the Ba-Er region. Model calculations using a shell correction approach with the axially deformed Woods-Saxon potential predict for 147Ba an octupole deformed ground state with β3 = 0.11.

A relativistic electron beam, generated by relativistic self-focusing of an ultra-high-intensity laser pulse in a He gas jet, was targeted onto high-Z materials for conversion to high-energy bremsstrahlung. Nuclear reactions in the primary converter materials as well as in secondary and tertiary targets placed directly behind the converter were analyzed with time-resolved γ-spectroscopy. The electron-jet temperature of more than 35 MeV, matching the giant dipole resonances of heavy nuclei, enabled us to efficiently generate photo-induced nuclear reactions. The measured temperatures are significantly higher than suggested by ponderomotive scaling. We supplemented our earlier measurement of the (γ, n) reaction cross section of 129I with a method solely based on nuclear reactions. The photo-induced transmutation yields were increased by two orders of magnitude compared to earlier experiments. Simulations with the Monte Carlo code MCNPX confirm the experimental results .

The VUV spectroscopic study of -particle-excited neon-krypton mixtures showed the occurrence of intense energy transfers from neon to krypton. The spectra of mixtures containing a few per cent krypton are similar to those of pure krypton. They are dominated by krypton's second continuum centred at 148 nm, its intensity increasing with the krypton concentration and the total pressure. Furthermore, a low-intensity emission due to the heteronuclear ion situated at 166.5 nm was also observed. The kinetic study of the second continuum of krypton revealed that heteronuclear reactions play an important role in the formation of at low krypton partial pressures. Their reaction constants were found to be for the state and for . Under high krypton pressures, homonuclear reactions were dominant, the reaction constant being for the state and for .

Measurements are made for variations of the effective secondary emission coefficient γ with reduced field E/p. Plane-parallel copper electrodes (5 cm diameter) are sustained with a dc voltage (0

The light pulses of two emissions of the molecule XeCl, centered at 308 and 345 nm, both have decay time constants that behave in a very similar way with respect to variations in the partial pressures of xenon and HCl; this is explained by collisional coupling between the states B and C of XeCl which are at the origin of the two emissions. The identification of the different collision processes and the determination of the reaction rate constants particularly underline the occurrence of a three‐body collision process between XeCl (B,C), Xe, and HCl; the rate constant is kM=(5.85±2.70)×10−5 Torr−2 ns−1. Measurements were also made of the coupling constants B→C and C→B which were found to be kBC=(2.56±1.05)×10−4 Torr−1 ns−1 and kCB=(1.45±1.05)×10−4 Torr−1 ns−1. The deduced energy gap between the two states (EB−EC=119 cm−1) is in very good agreement with the values in the literature.

In two-component Xe/HCl mixtures irradiated with alpha -particles, emissions centred at 308, 345 and 470 nm are observed; they correspond to the (B to X) and (C to A) transitions of XeCl* and to the transition (42 Gamma to 12 Gamma ) of Xe2Cl*, respectively. The Xe2Cl* emission was only seen when HCl was present as traces and Xe was at a pressure of over 200 Torr. The experiments showed the simultaneous presence of the emissions of the third continuum of xenon (290 and 390 mm) which compete with those of XeCl*. This implies that the Xe2+* ions and their precursors, which participate in the reactions of XeCl (B, C) formation are also at the origin of the third continuum. By means of intensity measurements, the energy gap between states B and C of XeCl was estimated at 118+or-40 cm-1.

For pt.I see ibid., vol.25, no.23, p.5141-8 (1992). In Ne-Xe mixtures molecular states responsible for the second continuum of xenon ( lambda =170 nm) are shown to be created by homonuclear and heteronuclear reactions from the 3P1 and 3P2 states of xenon. In Ar-Xe mixtures, at lambda =826 nm, two lines of argon and xenon are superimposed; it is observed that the atomic states responsible for the two transitions undergo decay (for argon) or creation (for xenon). The creation of the 2p10 xenon state is measured from the transition at lambda =980 nm which it produces. In the Ne-Xe mixture, at lambda =882 nm, it is the decay, through homonuclear and heteronuclear mechanisms, of the precursor 2p8 state of xenon which is demonstrated. In each case, the rate constants of the corresponding reactions are reported.

In a recent experiment [1] a high efficiency regime of stable electron acceleration to kinetic energies ranging from 10 to 40 MeV has been achieved. The main parameters of the electron bunches are comparable with those of bunches provided by commercial Radio‐Frequency based Linacs currently used in Hospitals for Intra‐Operative Radiation Therapy (IORT). IORT is an emerging technique applied in operating theaters during the surgical treatment of tumors. Performances and structure of a potential laser‐driven Hospital accelerator are compared in detail with the ones of several commercial devices. A number of possible advantages of the laser based technique are also discussed.

High-energy electrons can be produced in interactions of intense, ultra-short laser pulses with plasmas. Experiments conducted in the regime of moderate laser power (a few terawatts [TW]) are attracting increasing attention for their possibility of optimizing the acceleration process. Here we report the successful production of several-MeV electron bunches in interactions of femtosecond laser pulses from a 10 TW tabletop laser with supersonic gas-jets. The laser–plasma interaction and the obtained electron bunches have been characterized in detail, and conditions for stable and reproducible acceleration have been found. The accelerated electron bunches have been characterized by means of the measurement of the induced photo-activation of a gold sample via bremsstrahlung-generation of photons with suitable energy. The obtained result opens up a wide range of possible applications of the compact electron source for the concerns of nuclear physics studies. Some of them are briefly considered in this paper.

At wavelengths lower than 550 nm, addition of argon or neon to xenon gives rise to the emission of continua produced by heteronuclear processes (ArXe, Ne+Xe and NeXe+) indicating large energy transfers from the preponderant and lighter gas. Above 550 nm the transitions observed were all produced by atomic processes. Addition of argon to xenon causes an enhancement of certain xenon emissions ( lambda =770 nm in particular): this does not occur in Ne-Xe mixtures. These processes involve, above all, high energy states of xenon (configuration 5d). The kinetic study of certain emissions is dealt with in paper II (Galy et al., 1993).

At low pressures, excitation is due to the absorption of three photons and causes emission of the resonance line and the related first continuum ( lambda approximately 125 nm). At higher pressures, excitation mainly arises from a photon of the third harmonic of the laser wave and the second continuum ( lambda approximately 148 nm) is detected. Luminescence attenuations in the excitation spectra can be explained by the absorption of a fourth photon. The natural lifetime of the 3P1 is determined using Holstein's theory. The role of two and three-body collisions is demonstrated in the decay of the 3P1 state as in the role of three-body collisions for the 3P2 state. The corresponding rate constants are determined and the lifetime of the 1u(3P2) state evaluated.

A gamma-ray source with an intense component around the giant dipole resonance for photonuclear absorption has been obtained via bremsstrahlung of electron bunches driven by a 10-TW tabletop laser. 3D particle-in-cell simulation proves the achievement of a nonlinear regime leading to efficient acceleration of several sequential electron bunches per each laser pulse. The rate of the gamma-ray yield in the giant dipole resonance region (8

Electron and proton beams were investigated using a compact laser with intensities up to 2times1019 W/cm2 irradiating thin targets. For the direction of the electron beam theory and experiment disagree

A beam of MeV protons, accelerated by ultraintense laser-pulse interactions with a thin target foil, is used to investigate nuclear reactions of interest for spallation physics. The laser-generated proton beam is shown (protons were measured) to have a broad energy distribution, which closely resembles the expected energy spectrum of evaporative protons (below 50 MeV) produced in GeV-proton-induced spallation reactions. The protons are used to quantify the distribution of residual radioisotopes produced in a representative spallation target (Pb), and the results are compared with calculated predictions based on spectra modeled with nuclear Monte Carlo codes. Laser-plasma particle accelerators are shown to provide data relevant to the design and development of accelerator driven systems. © 2005 The American Physical Society.

Neutron production capabilities of table-top laser accelerated protons based on data from a high-energy single-shot large laser are addressed. Recently, McKenna et al (2005 Phys. Rev. Lett. 94 084801) have analysed the energy spectrum for a beam of protons accelerated on the VULCAN laser. In this paper, we present a new analysis of the same experiment which demonstrates, for the first time, production levels in excess of 109 neutrons per laser shot within a nanosecond pulse through (p,xn) reactions on lead targets. We have used this natPb(p,xn) conversion analysis approach to make predictions on the neutron production capabilities of table-top laser systems. Neutron spectra for current state-of-the-art table-top lasers have been calculated, and we have estimated that current systems are capable of producing 106 neutrons per second in nanosecond pulses. Furthermore, we have found that nanosecond neutron pulses at a rate of 5 × 109 neutrons per second are possible with the next generation of table-top lasers currently under construction., JRC.E.4-Nuclear fuels

Excited states in the 134Sb nucleus, populated in the β−-decay of 134Sn, have been studied at the mass separator OSIRIS. The 134Sn activity was produced via fast neutron-induced fission of 238U target. A main result was the discovery of a very low-lying first-excited state of 134Sb, at 13 keV, which has led to a strong revision of the level scheme. The new results are compared with different theoretical calculations and with the known data for the analogous neutron and proton two-particle nucleus in the 208Pb region. On the basis of this comparison, the energy of the (πg 7/2νf 7/2)7− isomer is estimated to be about 250 keV, some 100 keV lower than previously reported.

This experimental study concerns the secondary emission coefficient γ for two dielectrics (MgO and enamel) used in plasma display panels. Different pure rare gases were considered at pressures varying from 5 to 50 Torr. Here, we present the variations of coefficient γ as a function of the reduced field E/p. They were obtained by introducing the breakdown voltages measured experimentally on a sample of plasma panel, into the self-sustained equation. Concerning a 0.5 μm thick MgO layer, results are shown for five gases (helium, neon, argon, krypton, and xenon) whereas for a 25 μm thick enamel layer, they are presented for neon and xenon.

The authors have studied the excitation of the B2 Sigma u+ state of N2+ by energy transfer from neon in Ne-N2 mixtures at total pressures of several hundred torr. The decay of the light pulse corresponding to the transition nu '=O, nu "=O( lambda =391.4 nm) was reconstituted by means of the time-amplitude conversion method. The curves decrease exponentially. The variations of the decay time constant with the partial pressures of Ne and N2 enabled the kinetic scheme of the transfer process which uses Ne+ ions to be deduced.

The spectroscopic and kinetic study of argon and krypton luminescence is carried out using two complementary methods. Over the range of wavelengths from 200 to 800 nm, the optical spectrum of these gases, determined by means of a single photoelectron spectrophotometer, shows the presence of atomic lines and continuums. In the case of argon, between 400 and 500 nm, a weak continuum appears. This continuum had never been observed under similar experimental conditions. The decay of the luminosity is reconstituted by means of the time‐amplitude conversion method. The decrease of light of continuums is described by a difference of exponential terms. The variation of time constants with pressure allows the kinetic scheme which describes the mechanisms of the postluminescence to be deduced. The study of the continuums has confirmed the formation of diatomic molecules of rare gases as the result of triple collisions. The kinetic scheme is as follows: Al→k1 Al′+hν1, Al+2A→k3 A 2+A, and Al2→k′1 Al2+hν0 (continuum)....

The emission spectra of KrXe mixtures were plotted at different total pressures and at xenon concentrations varying from 0.5 to 99%. A characteristic emission of the mixture was seen at 490 nm, it appeared as soon as possible as the mixture contained 0.5% xenon. The emission at 490 nm has a maximum intensity at a xenon concentration of 20%. The shape of the light pulses obtained for this transition is described by an exponential decay with a time constant corresponding to the formation of the radiative state. The KrXe+ ion involved is the IV1/2 state; the kinetic scheme given defines the role and the value of the various reaction rate constants.

Spectroscopic study of KrXe mixtures shows large excitation energy transfers from krypton to xenon. When small quantitities of xenon are added to krypton, these processes can be seen through the fast disappearance of the continuous krypton emissions coupled with an increase in the atomic and molecular emissions of the minority gas. The excitation transfers are very efficient since the spectra of mixtures with only a few percent Xe are very similar in shape and intensity to those of pure xenon. Kinetic analysis of all the VUV emissions enabled a complete kinetic schema of the transfer phenomena to be drawn up. They are due to binary collisions from the molecular states, Kr*2(3Σu+), which are responsible for the second krypton continuum (k2=2.107 Torr−1 s−1) and from the atomic precursor states of molecular krypton (k1=7.106 Torr−1 s−1). Both processes have large cross sections. The two paths compete in the creation of resonant Xe(3P1) states, either through direct molecule–atom transfer or by atom–atom tra...

Selective excitation of the 6s'(1/2)1(1P1) state of xenon by three-photon absorption produces, in the VUV range, three characteristic emissions of xenon at 129, 147 and 173 nm. For pressures above 1 Torr, the excitation spectra are obtained for laser excitation wavelengths lower than the wavelength corresponding to three-photon resonant excitation of the 1P1 state in accordance with the negative dispersion wavelength zone where third harmonic generation is possible. The sharp drops in these excitation spectra are explained by a four-photon absorption process. From the temporal analysis of the emission at 129 nm, it is reasonable to infer that an ionisation phenomenon is involved which leads to the formation of an upper atomic state responsible for the formation of radiative molecular states by three-body collisions.

Selective excitation of xenon by multiphoton absorption of a dye laser beam gives, in the VUV, the emissions characteristic of this gas, i.e., the resonance line at 147 nm, the first continuum at 150 nm and the second continuum at 173 nm. The kinetic analysis of these emissions was carried out, using a correlation method, between 10−2 and 600 Torr. At low pressures the temporal variation of the density of the resonant 3P1 states allowed the resonance line trapping phenomenon to be demonstrated and the natural lifetime of these states to be determined (τn =4.3 ns). At high pressures the metastable 3P2 states are involved in the emission of the second continuum. The excitation spectra plotted for the blue satellite showed the creation of states in the 4f configuration. This phenomenon indicates that multiphoton ionization is not responsible for the creation of the metastable states. These states are created from a crossing of two molecular levels, one of which is bound (0+u) and responsible for the first co...

In the VUV range, the spectra of krypton, at pressures of a few hundred torr, consist of continuous emissions that are characteristic of Kr2* molecules. A time resolved study of the second continuum of krypton ( lambda =145 nm) has allowed the authors to establish a scheme of the formation and decay kinetics of the excited species that is responsible for this emission. The radiative molecular state has a lifetime of tau 2=250+or-20 ns, it is formed by two- and three-body collisions from an intermediate molecular state at a frequency 1/ tau 3=18.6 p2+3.9*103 p s-1 (p in torr).

The VUV luminescence spectra of argon excited by alpha particles at a few hundred Torr present two continua, at 180 and 127 nm. The 127 nm emission is very intense, it corresponds to transitions from the lowest vibrational levels of the A 1y(3 Sigma u+) and B Ou+(1 Sigma u+) states of Ar2 towards the dissociative X Og+(1 Sigma g+) ground state. The shape of the pulse corresponding to the emission of the second continuum was reconstituted by time amplitude conversion. Three exponential terms can be seen. The variation of the time constants with pressure allows a kinetic scheme for the formation and decay of the radiative molecule species to be established. The excited states of the argon molecule are created by three-body collisions, from the (1)()J=1 and (1)()J=2 states of the 3p54s configuration, the collision constants being 1.6 and 13.8 Torr-2 s-1 respectively. The radiative lifetime of the A 1u(3 Sigma u+) state is 2.86 mu s.

For pt.I see ibid., vol.15, p.2935 (1982). Spectroscopic and kinetic study of ultraviolet emissions from argon-xenon mixtures brings to light very large energy transfers from argon and xenon. When small amounts of xenon (a few ppm) are added to argon, the argon continua disappear and simultaneously Xe resonance lines can be seen. At higher Xe concentrations (of the order of a few per cent), the spectra of mixtures are similar to those obtained in pure xenon. Kinetic analysis of the main VUV emissions of the two gases allows a complete kinetic scheme of the transfer phenomena to be established. Excited radiative xenon states are created from Ar2* molecules and atomic precursor states. The 1P1 state of xenon is excited by two-body collisions with the excimer Ar2*(3 Sigma u+) which is responsible for the second argon continuum (k=1.5*107 Torr-1 s-1). The transfer is also observed from the Ar*(3P1) state towards highly excited xenon levels (configuration 5f) (k=2.4*107 Torr-1 s-1). Both these paths lead, directly or indirectly, to the production of the 3P1 and 3P2 states of xenon which, through three-body heteronuclear collisions, are involved in the formation of the radiative Xe2* states responsible for the emission of the second continuum at 173 nm. The lifetime of this state, tau =106 ns, is not modified by the presence of argon.

We study the destruction of N2C3Πu(ν′=0 and ν′=1) levels in mixtures N2–O2, N2–CO2, N2–CH4, and N2–H2O at total pressures of several hundred torr. The reciprocal of the time constant for the decay of luminous impulses, measured by time‐amplitude conversion, is a linear function of the partial pressures of the two constituents; for instance, τ−1=k1+k2pN2 +kxpx for the ν′=0 level, kx=0.9×10−2 torr−1·ns−1 (O2), 1.16×10−2 (CO2), 1.88×10−2 (CH4), and 1.36×10−2 (H2O). We compare the quenching cross sections obtained from kx with the ones of the kinetic theory. We indicate, lastly, that the energy liberated by C3Πu levels during the collision can be used for the formation of free radicals.

The experiment demonstrates at low pressure the resonant excitation of the 3P1 atomic state of xenon by three-photon absorption; as the pressure increases the xenon molecules in the ground state intervene in the absorption process. The emission spectra present the VUV continua characteristic of the excimer. In the same experimental conditions but with observation along the excitation axis, the frequency tripling phenomenon is seen close to the resonance line at 147 nm and the authors have measured new values of the phase matching parameter CXe between 145 and 147 nm.

A characteristic emission in the spectra of argon krypton mixtures can be seen at 640 nm. It reaches a maximum for krypton concentrations of about 30%. In argon xenon mixtures two emissions with the same origin are seen at 328 and 500 nm. The variation of their intensity with partial pressures is similar; a maximum is reached at a 10% Xe concentration. The shapes of the light pulses obtained at 640 nm in ArKR and at 328 nm in ArXe are described by an exponential decay relationship corresponding to the formation of the radiative state. In both cases the kinetic study shows that the emissions correspond to radiative transitions arising from the IV1/2 state of the heteronuclear ion which dissociates to the Ar(2P1.2) state; the various two- and three-body reaction constants relative to the atomic ion are calculated.

The far UV spectroscopic study of argon/kryptonmixtures demonstrates the very great efficiency of the Ar-Kr transfer processes. Kinetic analysis of the main molecular emissions of the two rare gases shows that the energy exchange essentially involves the molecular states of argon -the Ar2* species are destroyed on collision with krypton with an efficient cross-section of roughly 80 A2. The metastable Kr(3P2) states, which are an indirect result of the transfer, lead, through three-body heteronuclear collisions, to the formation of radiative Kr2* species which are themselves responsible for the emission of the continuum at 145 nm.

The results obtained in a xenon multiphoton excitation experiment using a pulsed dye laser are presented. At low pressures, the 3P1 resonant state of xenon is created by 3-photon resonant absorption. At higher pressures (> 20 torr), the excitation spectrum presents 2 components situated on either side of the resonance line. Spectral analysis in this region showed that they were continually originating from the molecular states A \( 1u\left( {{}^3\sum\nolimits_u^ + {} } \right)\) and B \( O_u^1\left( {{}^1\sum\nolimits_u^ + {} } \right)\) which are themselves related to the atomic 3P1 state. In the zone of negative dispersion of the medium we demonstrated the existence of a phenomenon of frequency tripling of the excitation laser beam. The light obtained in the direction of incidence is intense, the frequency can be tuned, and the band width is very narrow.

The results obtained in a multiphotonic excitation of xenon near the 6s'|1/2|1 state by a tunable pulsed dye laser are presented. At low pressure the lP1 resonnant state of xenon is created by 3-photon resonnant absorption. When the pressure increases, the excitation spectra widen and shift towards shorter wavelengths. We explain this phenomenon by an excitation of the Xe2 molecules in the ground state O+g towards molecular excited state 1u(1P 1 correlated to 1P1 state. A spectral analysis showed the presence in the luminescence of the first and second continuum of xenon. We demonstrated that the third-harmonic generation of the incident laser beam intervenes in the excitation process. This radiation was detected and his pressure dependance studied. The phase matching parameter cXe and the nonlinear susceptibility were measured.

The spectroscopic analysis of xenon at pressures between 50 and 700 torr shows the presence of several continuums over a wavelength range of 110–700 nm. The kinetics of two of them, 173 and 210 nm, are studied. In both cases, the shape of the light pulse, reconstituted by a time‐amplitude conversion method, is defined by a difference of two exponential terms. These terms represent the formation and the decay of the molecular species. The variation of the time constants with pressure allows the reaction constants of the various processes in the kinetic scheme to be found. The continuum in the vuv is brought about by the 3Σ+u state formed by three‐body collisions: k= (8.0±0.7)10−32 cm6 s−1 and the lifetime τ=102±2 ns; in the near uv, the molecular state has a shorter lifetime τ′1=8.2±0.5 ns but is formed like the previous one by three‐body collisions: k3= (2.3±0.06)10−30 cm6 s−1. The near uv xenon emission constants ave very close to those we previously reported for argon and krypton.