The results of rotationally resolved resonance enhanced multiphoton ionization photoelectron spectroscopy and zero kinetic energy-pulsed field ionization studies on HBr via various rotational levels of the F 1 ⌬ 2 and f 3 ⌬ 2 Rydberg states are reported. These studies lead to an accurate determination of the lowest ionization threshold as 94 098.9Ϯ1 cm Ϫ1. Observed rotational and spin-orbit branching ratios are compared to the results of ab initio calculations. The differences between theory and experiment highlight the dominant role of rotational and spin-orbit interactions for the dynamic properties of the high-n Rydberg states involved in the pulsed field ionization process.

We report the first multiphoton study of the electronic spectrum of the dimethyl sulfide molecule. The interpretation we present is based on analysis of the two-and three-photon resonance enhanced multiphoton ionisation (REMPI) spectra and measurements of the kinetic energies of the photoelectrons resulting from the REMPI process. Members of four (possibly five) Rydberg series are identified and a refined value of the first ionisation limit of dimethyl sulfide is obtained: E i = 8.710 & 0.005 eV (70250 & 40 cm-'). As in our previous study of the related divalent sulfide methanethiol, we detect the presence of slower electrons in the photoelectron spectra which can be interpreted in terms of near resonant inter-Rydberg state vibronic mixing.

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One-and two-color two-photon resonance enhanced multiphoton ionization spectroscopy of the d?hoofdlettersigmasup+ state of NH Wales, N.P.L.; de Beer, E.; Westwood, N.P.C; Buma, W.J.; de Lange, C.A. Published in:Journal of Chemical Physics DOI:10.1063/1.466791 Link to publication Citation for published version (APA):Wales, N. P. L., de Beer, E., Westwood, N. P. C., Buma, W. J., & de Lange, C. A. (1994). One-and two-color two-photon resonance enhanced multiphoton ionization spectroscopy of the d?hoofdlettersigmasup+ state of NH. Journal of Chemical Physics, 100, 7984-7994. DOI: 10.1063/1.466791 General rightsIt is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), other than for strictly personal, individual use, unless the work is under an open content license (like Creative Commons). Disclaimer/Complaints regulationsIf you believe that digital publication of certain material infringes any of your rights or (privacy) interests, please let the Library know, stating your reasons. In case of a legitimate complaint, the Library will make the material inaccessible and/or remove it from the website. Please Ask the Library: http://uba.uva.nl/en/contact, or a letter to: Library of the University of Amsterdam, Secretariat, Singel 425, 1012 WP Amsterdam, The Netherlands. You will be contacted as soon as possible. The ionization and dissociation processes occurring after two-photon excitation of the d '2' state of NH have been investigated using one-and two-color multiphoton ionization spectroscopy in combination with mass-resolved ion and kinetic energy-resolved electron detection. The photoelectron spectra obtained for ionization of the molecule via the d 'Z+ state (u ' =O,l) reveal a one-photon ionization process to all energetically accessible vibrational levels of the X 'Ii ground ionic state, at variance with a one-configuration description of the two states. Moreover, electrons are observed that derive from a one-photon ionization of excited neutral nitrogen and hydrogen atoms. Two-color excitation experiments of the d 'Z+ state show that the influence of discrete states at the overall three-photon level on the dissociation dynamics is insignificant. Using the results of ab initio calculations it is concluded that these experimental observations can be interpreted consistently if two competing processes are assumed to take place from the d '2+ excited state: a molecular one-photon ionization which is forbidden in zeroth order, and a two-photon nonresonance enhanced excitation to neutral (pre)dissociative states. I. INTRODUCTIONResonance enhanced multiphoton ionization in combination with photoelectron spectroscopy (REMPI-PES) has in the past been shown to provide a powerful tool for the study of the electronic character of excited states, and its consequences for subsequent photoionization dynamics. The studies performed recently on the imidogen radical (NH) may in this respect be considered as exemplary.'~2 In these studies two-p...

(3 + 1) resonance enhanced multiphoton ionization-photoelectron spectroscopy is employed to investigate the spectroscopy and ionization dynamics of the E, F, and G Rydberg states of CIO. The results establish that the E and F Rydberg states converge upon the X 3~-ground ionic state, while the G state belongs to a Rydberg series with an excited a ~A ionic core. Improved ionization thresholds of these two ionic states are determined as 10.887 _+ 0.005 and 11.750 _+ 0.005 eV.