Two-colour picosecond timeresolved (2 + 1C') resonance enhanced multiphoton ionization photoelectron spectroscopy on the B E1EC'C' and CC' E1AC1E" states of ammonia Dobber, M.R.; Buma, W.J.; de Lange, C.A. 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 picosecond predissociation dynamics of vibronic levels of the B and e' Rydberg states of ammonia have been investigated in real time by (2 + 1') two-color pump-probe ionization in combination with photoelectron spectroscopy. The picosecond real-time results are in reasonable agreement with the results obtained from indirect methods using nanosecond excitation. These indirect methods include investigations of the peak intensities and the natural line widths of the rotational lines in the excitation spectra. The photoelectron spectra obtained for (2 + 1) ionization via the B state in NH3 and ND3 are interpreted and shown to allow for an accurate determination of hitherto unknown vibrational frequencies in the ground state of NH3' (ND3+).For the VI symmetric stretch a frequency of 0.404 f 0.007 eV (0.304 f 0.007 eV) is found, while the frequency of the v4 asymmetric bend vibration has been established as 0.197 f 0.007 eV (0.141 f 0.007 eV). The hydrogen atom fragment, which results from the predissociation of the B and e' Rydberg states, has been detected in a two-color pump-probe experiment using nanosecond excitation.

Resonance enhanced multiphoton ionization photoelectron spectroscopy on nanoand picosecond timescales of Rydberg states of methyl iodide Buma, W.J.; Dobber, M.R.; de Lange, C.A. 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. Rydberg states of methyl iodide have been investigated using resonance enhanced multiphoton ionization in combination with photoelectron spectroscopy with nanosecond and picosecond laser pulses. The study of the ns (6~2~ 10) Rydberg states in two-, three-, and four-photon excitations has resulted in an unambiguous identification of state [l] in the 7s and 8s Rydberg states. As a consequence, it is concluded that the transition to 6s [l] in two-and three-photon excitations is anomalously weak. The application of photoelectron spectroscopy to identify the electronic and vibrational nature of a resonance has led to a major reinterpretation of the excitation spectrum of the 6p Rydberg state in two-photon excitation. In many of the recorded photoelectron spectra anomalous electrons are observed, which derive from a one-photon ionization process. This process is suggested to find its origin in the mixing of 6p and 7s character into higher-lying Rydberg states. The major difference between resonance enhanced multiphoton ionization photoelectron spectroscopy with nanosecond and picosecond lasers is found in a less effective dissociation of the molecule in the picosecond experiments. I. INTRODUCTIONThe excited states of methyl iodide have since long attracted considerable interest, both from an experimental and a theoretical point of view.lT31 Investigations of the dissociation occurring in the lowest excited dissociative states, the A band,tm2' and the predissociation of higherlying excited states to the A band23-30 have served as benchmark studies of the dissociation of an isolated molecule. Spectroscopic studies of the Rydberg states of methyl iodide, on the other hand, have allowed for a detailed characterization of properties such as the influence of spinorbit coupling and vibronic interactions,32-35 and the study of analogies of the quantum defects in molecules and rare gas atoms.3"39Methyl iodide is a molecule of C3, symmetry with a ground state electronic configuration . + *aTe4( 'A,). In the following we will, for reasons of convenience, ...

Resonance enhanced multiphoton ionization photoelectron spectroscopy and pulsed field ionization via the F 1D2(v'=0) and f 3D2(v'=0) Rydberg states of HCl Buma, W.J.; de Beer, E.; de Lange, C.A. 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. Download date: 12 May 2018Resonance enhanced multiphoton ionization photoelectron spectroscopy and pulsed field ionization via the F 'Aq(v'=O) and f 3A2(~'=0) (Received 22 February 1993; accepted 13 May 1993) In this paper, we report the first rotationally resolved one-and two-color resonance enhanced multiphoton ionization photoelectron spectroscopy (REMPI-PES) study of the HCl molecule. The agreement between our experimental branching ratios and theoretical investigations is excellent. We also report the first zero kinetic energy pulsed field ionization (ZEKE-PFI) experiments carried out in a "magnetic bottle" electron spectrometer. A direct comparison is made between ZEKE-PFI and REMPI-PES spectra for ionization via several rotational levels of the F 'Az(v'=O) and f 3Az(u'=O) Rydberg states of HCl. Large differences in both the spinorbit and rotational branching ratios are found between the ZEKE-PFI and REMPI-PES spectra. These differences can be understood qualitatively on the basis of rotational and spin-orbit autoionization mechanisms. I. INTRODUCTIONValuable information on the fundamental physics involved in molecular photoionization processes can be obtained from a detailed investigation of the ionic state branching ratios. In particular, rotational branching ratios are a direct measure of the angular momentum composition of the photoelectron, making them a sensitive probe of the ionization dynamics. Photoionization from the initial (ground) state may take place by absorption of a single vacuum ultraviolet (VUV) photon or via resonance enhanced multiphoton ionization (REMPI). When the latter technique is used, ionization of a selected rovibronic level of an excited state can be studied, thus significantly reducing the number of final ionic states accessed. With a resolution of several millielectron volts achievable in REMPI-PES, rotationally resolved spectra have only been obtained in a few cases, e.g., for the diatomic hydrides H2,1T2 OH,3 and NH495 and for the NO radical.6Recently, Miiller-Dethlefs et al.' dev...

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.

Conformational instability of the lowest triplet state of the benzene nucleus: I. The unsubstituted molecule van der Waals, J.H.; van Hemert, M.C.; Buma, W.J.