Photodetachment cross sections for WO−3 have been measured near the detachment threshold (3.0–3.7 eV). A fast beam of WO−3 is merged with a coaxial cw laser beam and the photodetached electrons are detected with a magnetic confinement slow electron collector. The photodetachment spectrum yields an electron affinity for WO3 of 3.33+0.08−0.15 eV, somewhat lower than values obtained in thermodynamic equilibrium measurements. In addition, a lower limit of 3.7 eV is obtained for the electron affinity of HWO4.

The accuracy for the direct measurement of the dissociation energy of the N~ B e 22, +-state was significantly improved by using frequency doubled laser light, which enables the authors to excite from lower v"-levels and additionally to calibrate the fundamental laser wavelength with an iodine cell. The obtained value is: D s (N~) = 70248 +_ 6 cm-1.

A translational spectroscopy technique is used to obtain predissociation kinetic energy release spectra from the lowest bound states of H3, 2s 2A′1 and 2p 2A″2. These H*3 states are formed in near-resonant electron capture by 3 keV H+3 in Cs vapor. Their ground rovibrational levels are energetically about 1 eV above the H+H+H dissociation limit, thus all levels can yield both H2+H and the three-body products. The spectra contain both three-body and two-body components and are deconvoluted to obtain the branching ratios. Data obtained from two different ion sources show that the three-body/two-body ratio increases with increased rovibrational energy in the H*3. The results are compared to recent theory and with previously reported ratios from dissociative recombination of H+3. The comparison suggests that the ratio increases monotonically with the total electronic and rovibrational energy in the H*3. D*3 predissocation has a similar behavior. The H- and D-atom spectra from the two-body decay of HD*2 show that the ejected H atom is strongly favored on a per-atom basis.

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.

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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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