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The laser-induced fluorescence excitation spectra of jet-cooled CuF have been recorded in the range of 19000-21470cm-1, in which the CuF radicals were produced by the reaction of SF6 with copper atoms from a dc discharge-sputtering source under supersonic jet conditions. Eight observed vibronic transition bands have been assigned as the transition from the ground state X(1Σ+) to B(1Σ+), C(1Π) and an unreported upper state. The rotational structure of all observed bands has been analysed at the estimated rotational temperature 80K. We determined the newly observed band to be the (1Π,v = 1)-X(1Σ+v = 0) transition according to the character of the rotational structure and the isotopic shift analysis. In addition, the lifetimes of the states involved in these bands were measured.

The laser-induced fluorescence excitation spectrum of the A2Σ--X2Π3/2 transition of CuO in the 540-620nm region has been studied, where the CuO molecule was produced by using the technique of dc discharge reaction under a supersonic condition. We have recorded and rotationally analysed the 0-0, 1-0, 2-0 and 3-0 bands. The rotational constants of the upper state A2Σ- were determined and vibrational constants improved. In addition, the lifetime measurement for the A2Σ- state was carried out under the collision-free condition and the lifetimes obtained are 469±2, 456±2, 488±3 and 490±4ns for v'=0, v'=1, v'=2 and v'=3 levels, respectively.

The resonance-enhanced multiphoton ionization (REMPI) spectra of atomic chlorine and bromine in the range of 230-245 nm and 250-285 nm were obtained by using REMPI and time of flight (TOF) techniques. There are twenty-six lines for Cl and twenty-three for Br in the spectra, among which five transitions of Cl and four of Br are observed for the first time. These lines are due to transitions from the Cl(3p 2P3/20, 2P1/20) and Br(4p 2P3/20, 2P1/20) states to upper states induced by two-photon excitation. It is found that the Stark shift of different excited states are almost the same, and they are independent of the S, L, and J quantum numbers of the excited state.

In this paper, by using resonance enhanced (2+1) multiphoton ionization (REMPI) of AsH3 and detecting the daughter molecular ions AsH+ and As+, a long progression discrete structure was obtained from 267 to 291 nm, which obeys the formula v0(cm-1)=68875.3+504.1v'2+5.26v'22. Analysis of the spectrum has revealed that it belongs to 4d Rydberg state transition. Our assignment yields the 4d Rydberg state parameters Te'=67881.1 cm-1, we'=495.1 cm-1 and δ=0.962. Finally the 4d Rydberg state structure of AsH3 was discussed.

Laser-induced fluorescence excitation spectrum of B2Σ＋— X2Σ+ transition of gas-phase AlO radical cooled in a supe rsonic jet has been observed in the range of 430—480nm.AlO was produced by reac ting O2 with Al atoms from a dc discharge-sputtering source.The obser ved vibrational bands were identified as V′-V″=1,2,3 transitions respectively. The vibrational frequencies and anharmonic constants were obtained for both the ground state X2Σ+ and the excited state B2Σ+.Furthermore a rotational analysis of the (1,4) band was made.The abno rmal intensity of the V″=5 transitions is discussed.

The dynamics of photon-dissociation of PCl3 in the range of 265—285nm was studied by using tunable dye laser. The measured emission spectra are similar in this excitation range, but their intensities are different. Three main peaks are observed in the range of 380—520nm in the emission spectrum. The strongest peak is at 43lnm, the other two weaker peaks are at 389 and 488nm, respectively. It is suggested that the peak at 488nm is from the transition of PCl(A) to PCl(X), and the peaks at 431 and 389nm are from the transitions of a new singlet state PCl(c?) to PCl(b) and PCl(a), respectively.

About 50 spectral lines due to the (2+1) resonance-enhanced multiphoton ionization (REMPI) of atomic sulfur, generated in the sequential multiphoton dissociation of SO2 at probing wavelengths, in the 243—263 nm region has been observed. Besides most of the lines which are due to the two-photon transition from the ground states 3P2,1,0 to the Rydberg states 3P, 3D, 3F until n=10 of S atom, several new lines including the spin forbbiden transition 1P0, 5S0←3P and the two-photon transitions from the excited state 1D2 to the Rydberg states np1,3D, 1,3F are observed. Intensities of some lines have been calculated and compared with the experimental results.

The influence of the different gas ratios (SO2/Ar) on the vibronically resolved laser-induced fluorescence excitation spectra of the SO2( 1A2— 1A1) system was investigated under the supersonic jet conditions.High resolution spectra of two complete progressions (1,m,1),(0,n,1) were obtained,in which the rotational structures of the (0,9,1),(0,10,1),(1,7,1),(1,5,1)-(0,0,0) bands were observed,for the first time,so long as we know.The assignments of 847 rotationally resolved lines were based on an asymmetric top simulation,which results in the determination of the rotational and centrifugal distortion constants of each vibrational level of state.The approximate geometry parameters of state was derived to be r(S—O)=0.160nm,∠OSO=101.64°.In addition,a discussion on the inertial defect of each vibrational level of state was presented.

The (2+1) resonance-enhanced multiphoton ionization (REMPI) spectra of the CF2Cl radicals, which are generated by a pulsed dc discharge,were investigated between 332 and 362nm.Two new Rydberg states,4s and 4p,were observed and indentified.The observed states and spectroscopic constants include 4s Rydberg state (band origin ν0—0=55371cm-1,ω3′ (CF2 scissors)=523±7cm-1,ω′4 (OPLA,i.e.,out-of-plane bending mode)=734±4cm-1) and 4p Rydberg state (ν0—0=57601.3cm-1,ω3′=552±10cm-1,ω4′=762±12cm-1).The quantum defect values of 4s and 4p Rydberg states were also estimated.It seems that the radical production by a pulsed dc discharge combined with PEMPI technique is a powerful tool to study the electronic state of radicals.

Combing the techniques of supersonic molecular beam and vacuum ultraviolet synchrotron radiation photoionization time-of-flight mass spectroscopy,we have measured the photoionization efficiency(PIE)curves of ions from (CH3I)n(n=1,2,3,4)cluster molecules and obtained the adiabatic ionization potentials of (CH3I)n+(n =1,2,3,4) and appearance potentials of the fragment ions.From these data,bond energies D0 of the related molecules or molecule ions have been evaluated.Several autoionization structures of CH3I in the PIE curve of CH3I+ have been observed and 4 Rydberg series,ns,npσ, npπ and nd, converging to CH3I+(2Ｅ1/2),are identified.

The vibrational autoionization stucture of dibromomethane has been investigated in the supersonic beam conditions using ＶＵＶ synchrotron radiation. Based on photoionization efficiency curve of ＣＨ 2 Ｂｒ 2 + in １０５—１２３ｎｍ we have found that the adiabatic ionization potential(IP) of the dibromomethane is １０.２３±０.０１ｅＶ．The thresholds at １０.７８±０.０１ｅＶ，１１.２０±０.０１ｅＶ and １１.２７±０.０１ｅＶ ware identified as the electronically excited states of ＣＨ 2 Ｂｒ 2 + ,i.e., Ａ（ 2 Ａ 2 ），Ｂ（ 2 Ｂ 1 ） and Ｃ（ 2 Ａ 1 ） states. The discrete peaks with some autoionization features superposed on a step-like structure in the PIE curve of the parent ion were observed in the range of １１５.０１—１２１.１５ｎｍ. The average step width was about ７１６.８±４０.０ｃｍ -1 ，which was in good agreement with the value of the vibrational frequency of the Ｂｒ-Ｃ-Ｂｒ antisymmetrically stretching motion （ｖ 9 ） of the parent ion ＣＨ 2 Ｂｒ 2 + （Ｘ 2 Ｂ 2 ) which was measured by infrared absorption method. All strong peaks ware assigned to the autoionization, ｎｓ，ｎｐ and ｎｄ Ｒｙｄｂｅｒｇ states converging to various vibrationally excited states of the ground state of ＣＨ 2 Ｂｒ 2 + . In addition, the vibrational modes and autoionization structure occurring in the ground electronic state of the daughter ion ＣＨ 2 Ｂｒ + （Ｘ）were also assigned.

We present the first direct measurement of the absolute third-order rate constant for the reaction Na + OH + He → NaOH + He. OH(X2Π) was generated by the repetitive pulsed irradiation of H2O vapour through CaF2 optics in the presence of He and an excess of atomic sodium derived from a heat-pipe oven and comprising part of a slow-flow system, kinetically equivalent to a static system. Ground-state OH was monitored by time-resolved molecular resonance fluorescence at λ= 307 nm [OH(A2∑+–X2Π), (0,0)] following optical excitation using pre-trigger photomultiplier gating, photon counting and signal averaging. Na(3 2S1/2) was monitored in the steady mode using atomic resonance fluorescence at λ= 589 nm [Na(3 2PJ)–Na(3 2S1/2)] coupled with phase-sensitive detection. The following absolute third-order rate constant (T= 653 K) was obtained: k1(Na + OH + He)=(1.07 ± 0.21)× 10–30 cm6 molecule–2 s–1. Quantitative extrapolation to high temperatures using the unimolecular reaction rate theory developed by Troe yields the result k1(Na + OH + He)=(4.7 ± 1.0)× 10–26T–1.65 cm6 molecule–2 s–1. Furthermore, modifications to these calculations for flame conditions (M) indicate that k1(Na + OH + M) lies in the range (1–5)× 10–31 cm6 molecule–2 s–1 at 2000 K. This is significantly different to the values of k1 derived from modelling in flames. The role of Na + OH + M in flames seeded with atomic sodium is considered in this paper.

We present a kinetic study of the reactions of the OH radical with the molecules HCl and DCl over the temperature range 300–700 K in order to investigate the ‘intermediate’ region between room-temperature measurements and flame investigations. Ground-state OH radicals were generated by the repetitive pulsed irradiation of H2O vapour in a flow system, kinetically equivalent to a static system, and monitored in the time-resolved mode by resonance fluorescence at λ= 307 nm [OH(A2∑+→X2Π), (0, 0)] following optical excitation. Decay profiles of the OH radical in the presence of HCl and DCl were constructed following pre-trigger photomultiplier gating, photon counting, signal averaging and computerised analysis. A specially constructed high-temperature stainless-steel reactor, particularly designed for photon-counting measurements on a high-temperature system and critical to the extension of previous rate measurements of such reaction of OH by ca. 250 K, is described in detail with particular emphasis for procedures for minimising large background photon counts normally encountered in this type of system. The resulting rate data obtained in this investigation for the range 300–700 K may be summarised in the Arrhenius forms: OH (X2Π)+ HCl: kR=(2.94 ± 0.48)× 10–12 exp[–(446 ± 32)/T] cm3 molecule–1 s–1, OH (X2Π)+ DCl: kR=(4.04 ± 0.74)× 10–12 exp[–(718 ± 33)/T) cm3 molecule–1 s–1.These data are compared with the results of temperature-dependent studies that have been carried out by direct monitoring of the OH radical, employing both resonance absorption and resonance fluorescence of OH(A–X), on pulsed systems and discharge–flow systems up to temperatures of 460 K. The extrapolation of these results to flame temperatures, for which rate data for the reaction between OH + HCl have been reported from mass-spectrometric sampling of stable molecules, is considered in some detail. The temperature dependence of the diffusional loss of OH(X2Π), which dominates removal of the radical in the absence of HCl or DCl, when fitted to the standard form kdiff=C + n ln (T) yields n= 1.77 ± 0.14. Estimates of the geometrical parameters for light collection of the resonance fluorescence signal, coupled with the measured temperature dependence for diffusional loss, in turn yields D12(OH—He)= 0.28 ± 0.06 cm2 s–1 at s.t.p. The observed temperature dependence is further considered quantitatively in terms of the appropriate Lennard-Jones parameters for interaction.

We present the first direct measurements of the absolute third-order rate constant (k2) for the reaction Rb + OH + He → RbOH + He. OH(X2Π) was generated from the repetitive pulsed irradiation of H2O vapour through CaF2 optics in the presence of an excess of atomic rubidium, derived from a heat-pipe oven, and helium buffer gas. The decay of ground-state hydroxyl radical was monitored by OH(A–X) resonance fluorescence following optical excitation in a flow system, kinetically equivalent to a static system, using signal averaging. Atomic rubidium was monitored in the steady mode via the Rydberg transition, Rb(6 2PJ–5 2S1/2), at λ= 421 nm using phase-sensitive detection. The following value for k2 was obtained: k2=(8.8 ± 1.3)× 10–31 cm6 molecule–2 s–1(T= 490 K). This was extrapolated to high temperatures (2000 K) using the unimolecular reaction rate theory developed by Troe and incorporating, in a quantitatively detailed manner, the effects of hindered rotation on the low-frequency bending modes of RbOH. The extrapolations for the previous rate measurements we have reported for the analogous reactions involving Na and K have been reanalysed to include the effects of hindered rotation in the same manner, yielding the following forms for the recombination rate constants (kR): [graphic omitted]. The rate data extrapolated to 2000 K are also considered in terms of the role of alkali-metal hydroxides and alkali-metal atoms in flame inhibition.

We present the first direct measurement of the absolute rate constant for the third-order reaction K + OH + He → KOH + He. A complex experimental system is described in which a heat-pipe oven, from which atomic potassium is generated, is coupled to a high-temperature reactor for time-resolved resonance-fluorescence measurements on OH following pulsed irradiation. The apparatus is a slow-flow system kinetically equivalent to a static system. Atomic potassium is monitored in the steady mode using resonance fluorescence of the Rydberg transition at λ= 404 nm K[(5 2PJ)–(4 2S1/2)] coupled with phase-sensitive detection. Ground-state OH(X2Π), generated by the repetitively pulsed irradiation of water vapour, is monitored in the time-resolved mode at λ= 307 nm [OH(A2∑+–X2Π), (0, 0)] using molecular resonance-fluorescence measurements following optical excitation with pre-trigger photomultiplier gating, photon counting and signal averaging. Thus the decay of OH(X2Π) as a function of time is studied both as a function of [K(42S1/2)] and [He], yielding the absolute rate constant k3(K + OH + He)=(8.8 ± 1.8)× 10–31 cm6 molecule–2 s–1(T= 530 K). A full account is given of the isolation of this reaction by the use of a ‘chemical window’ through the control of temperature and the effective elimination of the reaction between K2+ OH, and the use of He as the third body which demonstrates negligible collisional quenching efficiency with OH(A2∑+, v′= 0). We also present a detailed extrapolation of the rate data to the environment of flames using unimolecular-reaction-rate theory developed by Troe and coworkers for dissociation reactions. The agreement between the present results for the isolated reaction extrapolated to flame temperatures and measurements on flames (1800 < T/K < 2200), in which k3(K + OH + M)(where M stands for the burnt gases of a fuel-rich flame) has been extracted by modelling the complex coupled equilibria, is considered highly satisfactory. Quantitative account of the modelling of the dissociation of KOH is presented in the paper.

We present a direct kinetic measurement of the absolute third-order rate constant for the reaction Cs + I + He → CsI + He. (1) I(52P3/2) was generated by the repetitive pulsed irradiation of CsI produced in a flow system from the reaction of CH3I in the presence of excess atomic caesium derived from a heat-pipe oven. The ground-state iodine atom was monitored by time-resolved atomic resonance fluorescence at λ= 178.3 nm {I[5p46s(2P3/2)]–I[5p5(2P3/2)]} using photon counting in the vaccum ultraviolet region. Cs(62S1/2) was monitored by steady atomic resonance fluorescence of the Rydberg doublet at λ= 457 nm [Cs(72PJ)–Cs(62S1/2)] using phase-sensitive detection. We report a measured absolute third-order rate constant of k1(T= 491 K)=(7.9 ± 1.2)× 10–31 cm6 atom–2 s–1, which we believe to be the first measurement of its kind. We also report an estimate of the rate constant for the reaction I + Cs2→ CsI + Cs (3) of k3(T= 491 K)≈ 2 × 10–10 cm3 molecule–1 s–1, which is found to be in accord with previous kinetic measurements on I + Na2 and Br + K2. The crossing between the covalent and the ionic surface, described by the Rittner potential function, is found to take place at 17.3 A, and hence the recombination is governed by the large impact parameters involved on collision. Consideration of the splitting between the two surfaces, coupled with the Landau–Zener formalism and Monte Carlo calculations of trajectories on those surfaces, yields a good quantitative account of the observed kinetic behaviour, not only of the present recombination measurements but also of shock-tube data that have been reported for the dissociation of CsI at elevated temperatures (2400 K). In view of this, despite the clear third-order kinetic behaviour observed here for reaction (1), detailed theoretical consideration of the ‘fall-off’ pressure regime found to satisfy both the present measurements and the shock-tube data leads to the preferred value of k1(T = 491 K)= 9.1 × 10–31 cm6 atom–2 s–1(±25%). The combination of the recombination and dissociation-rate measurements and the modelling calculations lead to the temperature dependence of the form k1(491 < T/K < 2400)= 4.1 × 10–30T–0.24 cm6 atom–2 s–1.

We present the first direct measurement of the absolute third-order rate constant (k1) for the reaction Cs + OH + He → CsOH + He (T= 481 K) completing the series of analogous studies with the present experimental system we have also described for Na, K and Rb. OH(X2Π), generated by the pulsed irradiation of H2O vapour through CaF2 optics in a slow-flow system, kinetically equivalent to a static system, was monitored by time-resolved resonance fluorescence at λ= 307 nm [OH(A2Σ+–X2Π), (0, 0)] in the presence of an excess of atomic caesium derived from a heat-pipe oven and helium buffer gas. The atomic caesium was monitored in the steady mode using atomic resonance fluorescence of the unresolved Rydberg doublet at λ= 457 nm [Cs(72PJ– 62S1/2)] coupled with phase-sensitive detection. The following value of k1 was obtained: k1(481 K)=(10.0 ± 1.5)× 10–31 cm6 molecule–2 s–1. This result was extrapolated to 2000 K using the unimolecular reaction rate theory by Troe, including the quantitative effects of hindered rotation on the low-frequency bending modes of CsOH. We have employed the same formalism to calculate the rate constant for the reaction between Li + OH + He at 500 and 2000 K. The resulting calculated temperature dependences of the third-order rate constants (kR) for the reaction X + OH + He → XOH + He are thus compared: [graphic omitted]. Extrapolation of the rate data to flame conditions is considered with particular emphasis on the role of H2O as a third body in recombination reactions of this type. It is concluded that a reassessment of the standard collisional deactivation efficiency, βc, for H2O at elevated temperatures can be used to reconcile former differences between recombination rate data extrapolated from measurements of the present type with those derived from modelling on flames.