Two-Color Picosecond Time-Resolved (2 + 1') Resonance-Enhanced Multiphoton Ionization Photoelectron Spectroscopy on the B1E'' and C' 1A1' States of Ammonia

Abstract

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.

Time-resolved photoelectron spectroscopy of the allyl radical: The lifetimes of the ultraviolet bands

“…Such a rotational dependence was for example reported in a ps time-resolved study of predissociation lifetimes in the B-and C-state of ammonia, where significantly different lifetimes were reported for high or low JЈKЈ values. 40 In the case of allyl with two small rotational constants 3 (BЉϭ0.346 cm Ϫ1 , CЉϭ0.290 cm Ϫ1 ) it is not possible to excite individual J-states even with pulsed ns-dye lasers. On the other hand, due to the relatively large constant AЉϭ1.802 cm Ϫ1 , the K-structure was partially resolved in the ns-MPI spectra, permitting a simulation of the rotational band contours.…”

“…40͒ and CH 3 I. 41 Just recently the technique was extended to transient species in studies on I 2 Ϫ and I 2 Ϫ ͑H 2 O) x clusters. 42 Here we demonstrate the application of time-resolved spectroscopy in a magnetic bottle to medium-sized organic hydrocarbon radicals.…”

Energy- and angle-resolved pump–probe femtosecond photoelectron spectroscopy: Molecular rotation

“…[5][6][7][8] This advantage of time-resolved photoelectron spectroscopy has already been well demonstrated in the picosecond domain. [12][13][14] Its potential for probing molecular dynamics in the femtosecond regime has also been exploited experimentally for several systems. [5][6][7]15 Furthermore, Davies et al 8 have recently reported results of the first femtosecond photoelectron-photoion coincidence imaging studies of photodissociation dynamics.…”

The spectroscopy of high Rydberg states of ammonia

“…Our knowledge of the predissociation dynamics of vibrational levels of the B state in NH 3 and ND 3 has been extended subsequently by (2ϩ1Ј) two-color pump-probe ionization on a picosecond time scale in combination with high-resolution photoelectron spectroscopy. 24 Clarification of the extent of Jahn-Teller distortion affecting the degenerate B state has come from a number of rotationally resolved double resonance studies in which B state levels associated with excitation of one quantum of each of the doubly degenerate vibrations 3 Ј and 4 Ј , 25 built on a progression in 2 Ј , were populated following initial excitation of molecules into selected rovibrational levels of the X [26][27][28] or à 29,30 states. These studies also showed that the historically labeled C -X system of ammonia actually involves a vibronic component of the B state.…”

“…31͒ and sub-Doppler 2ϩ1 32 REMPI techniques as well as real-time pump-probe REMPI-PES studies on a ps time scale. 24 Analysis of the widths and intensities of individual rovibrational features in the C Ј-X multiphoton excitation spectrum provided evidence for two competing predissociation mechanisms: a homogeneous predissociation ͑i.e., involving coupling to one or more states of the same vibronic symmetry, the efficiency of which is thus independent of parent rotation͒ presumably involving the à 1 A 2 Љ state, and a heterogeneous route promoted by in-plane ͑x,y axis͒ rotation which was attributed to Coriolis induced predissociation via the B 1 EЉ state. These data, quantum defect considerations, and the results of companion REMPI-PES experiments [33][34][35] which show a strong propensity for the final one-photon ionization step to be Franck-Condon diagonal in all vibrational modes, all indicate that the C Ј 1 A 1 Ј state is the first (nϭ3) member of the npa 2 Љ←1a 2 Љ Rydberg series of ammonia.…”