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The direct photodissociation process SO + a 41I + h v ~ S + (4S°)+ O(3P) via the repulsive SO + 1 42+ state has been studied using a laser-ion photofragment spectrometer with coaxial beams. The kinetic energy distribution of the S + photofragments has been measured at a laser wavelength of 2 = 488 nm (h v = 2.54 eV). The spectrum shows vibrational structure which can be assigned to transitions from the vibrational levels v=7-13 of the initial a 4//state. The experimental data are used along with semi-empirical calculations to locate the potential curve of the repulsive 1 4Z+ state in the Franck-Condon region. The results are compared with data obtained from photopredissociation studies of SO + and with theoretical calculations for the 1 42 + state.

Photofragment spectroscopy of N~-has been studied in the wavelength range 343~404 nm using an excimer-pumped dye laser with a spectral resolution of 0.2 cm-1. The observed bands are assigned to transitions from the v" =23-26 levels of the X2S~ state to highlying rovibrational levels (v'~ 46-48) of the B 2S,+ state, forming quasibound (predissociating) states above the dissociation limit N+(3P)+ N(4S°). Measurement of the photofragment kinetic energies allows to establish an absolute energy scale for the transitions with respect to the dissociation limit. Molecular constants for the lower and upper states of the observed transitions are determined. The measurements allow the first direct determination of the N2 + dissociation energy Do°(N~-). Some high-resolution (0.04 cm -1) measurements show the fine-structure splitting and lifetime broadening of the excitation lines.

Abstract. The direct photodissociation process SO + + h v ~S + + O has been studied using the technique of ion photofragment spectroscopy. The kinetic energy distribution of the S photofragments has been measured for selected wavelengths in the range )~ = 308-514.5 nm. Transitions from the metastable a4H state to the dissociative 1 427 + state as well as from the X2H ground state to a higher-lying 2H state have been observed. From the vibrationally resolved kinetic energy spectra, the potential curve of the repulsive 1 4X + state has been determined for the range of internuclear distances R = 3.0-4.5 a 0. In addition, the analysis gives the vibrational population of the SO + (a4H) ions after dissociative electron-impact ionization of SOs in the low-pressure monoplasmatron ion source.

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