(2+1) resonance-enhanced multiphoton ionization–photoelectron spectroscopy of the OH radical

Abstract

A (2+1) resonance-enhanced multiphoton ionization–photoelectron spectroscopy (REMPI-PES) study of the OH radical has been carried out in the two-photon energy region between 81 300 and 88 900 cm−1. Translationally and rotationally hot OH radicals are generated via photodissociation of hydrogen peroxide or formic acid. The known D 2Σ− (v′=0–2) and hitherto unobserved 3 2Σ−(v′=0) intermediate states in this region (at 81 815.8 and 87 643.7 cm−1 above the ground state) are shown to possess predominant Rydberg character. From the rotational structure in the REMPI spectrum physical parameters have been derived for these states.

Photoion rotational distributions from near-threshold to deep in the continuum

“…These l-changing collisions strongly influence the ion rotational distributions in molecular photoionization. This point has been discussed in REMPI-PES studies 5,6,[41][42][43] and ZEKE-PFI investigations 10,40,76 and is even more important in the context of these energy-dependent studies. The present fluorescence measurements allow us to see how this underlying dynamical behavior evolves with energy.…”

“…One method is to select H 2 or another diatomic hydride with a large rotational constant. 5,[41][42][43]45,46 Another technique is to use the first stage of the REMPI process to state-select a high-N level, so that the spacings between adjacent rotational levels are comparatively large and can be resolved via time-of-flight photoelectron spectroscopy. 6,34 -36 These REMPI-PES strategies exploit laser technology to go beyond the limits of earlier resonance lamp studies.…”

“…While dipole selection rules constrain the angular momentum of the photoelectron-photoion complex, the partitioning of angular momentum between the electron and ion is governed by the ionization dynamics. [5][6][7][8][9][10][11][12][13]29,[33][34][35][36][37][38][39][40][41][42][43][44][45][46][47] Conservation of angular momentum dictates that the change in core angular momentum is restricted by 10 Excluding electron spin, the change in angular momentum, ⌬N, is hence given by ⌬NϭN ϩ ϪN 0 ϭ͑lϩ1 ͒,l,...,Ϫ͑lϩ1͒. ͑2͒…”

Mass spectrometric and laser spectroscopic characterization of a supersonic planar plasma expansion

“…Plasma jet expansions have been used as a powerful technique for high resolution spectroscopy of molecular transients [1][2][3][4][5]. In recent years rotationally resolved spectra have been recorded for a number of radical and ionic species, combining plasma expansion techniques and sensitive spectroscopic detection techniques, such as LIF [1], REMPI-TOF [2], REMPI-PES [3], photo-detachment [4] and vibrational predissociation [5] spectroscopy.…”

“…In recent years rotationally resolved spectra have been recorded for a number of radical and ionic species, combining plasma expansion techniques and sensitive spectroscopic detection techniques, such as LIF [1], REMPI-TOF [2], REMPI-PES [3], photo-detachment [4] and vibrational predissociation [5] spectroscopy. In the case of direct absorption experiments planar plasma expansions, i.e., expansions through a long and narrow slit, have turned out to be particularly useful.…”