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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.