Rotational state distributions from vibrational autoionization of H2 revisited

Photoionization dynamics in CS fragmented from CS2 studied by high-resolution photoelectron spectroscopy

The photoionization dynamics of CS have been studied using high-resolution laser photoelectron spectroscopy. The photodissociation of CS2 at ~308 nm results in highly rotationally excited CS in its X1Σ+ singlet ground state, as well as in rotationally cold CS in the excited a3Π triplet state. The ground-state CS fragments are formed together with sulfur in its 3P, 1D, and 1S electronic states; triplet CS is produced in coincidence with ground-state sulfur (3P). In both channels the photoelectron spectra are dominated by Δv = 0 propensity, but transitions involving Δv = 1 and 2 are also observed. Key words: photoelectron spectroscopy, photoionization, photodissociation, excited states, reactive intermediates.

Ion rotational distributions following vibrational autoionization of the Rydberg states of water

Double-resonance laser excitation and high-resolution energy dispersive photoelectron spectroscopy were used to determine the ionic rotational-state distributions following vibrational autoionization of Rydberg states of water having principal quantum number n=8-10 and converging to the X (2)B(1) (1,0,0) state of H(2)O(+). Where possible, these states were identified by comparison with results of a calculation based on multichannel quantum defect theory. Symmetry and angular momentum constraints link the observed ionic rotational states to particular values of the orbital angular momentum of the Rydberg electron, l, and to the partial-wave composition of the ejected electron. In particular, this connection allows an unambiguous determination of the even or odd character of the partial waves and provides a test of the predicted character of the autoionizing resonances. The effects of l mixing induced by the nonspherical nature of the ionic field are plainly evident in the ion distributions. The present results also allow a tentative assignment of some resonances to the previously unidentified np Rydberg states.

Mode dependent vibrational autoionization of Rydberg states of NO2. II. Comparing the symmetric stretching and bending vibrations

Triple-resonance excitation and high-resolution photoelectron spectroscopy are combined to characterize the mode selectivity of vibrational autoionization of the high Rydberg states of NO2. Photoelectron spectra and vibrational branching fractions are reported for autoionizing Rydberg states converging to the NO2+ X 1Sigmag +(110) state, that is, with one quantum in the symmetric stretch, nu1, and one quantum in the bending vibration, nu2. These results indicate that autoionization proceeds most efficiently through the loss of one quantum from the symmetric stretch rather than from the bending vibration. The implications of this result are discussed in terms of the autoionization mechanism.