IR-MPE/D dynamics studied by pulsed VUV laser photoionization

Abstract

One-photon ionization by a pulsed VUV laser has been employed to probe infrared multiphoton excitation and dissociation (IR-MPE/D) dynamics in real time, in situ, and collision free during excitation by a CO2− laser pulse. In this first experiment acetic anhydride has been used as the parent molecule to demonstrate the feasibility and to study properties of the method. Using the 118.4 nm radiation from a VUV laser as source for photoionization, ions have been observed mass selectively with time resolution in the nanosecond range, determined by the laser pulse duration. By following production and decay rates of ions, the time dependence of the excitation and decay of parent molecules, and the evolution of neutral intermediates in primary and sequential steps could be observed, from which detailed information on excitation and dissociation pathways was deduced.

Resonant Ionization Using IR Light: A New Tool To Study the Spectroscopy and Dynamics of Gas-Phase Molecules and Clusters

“…In our experiments on Ti, V, Nb, and Zr carbide clusters, no larger clusters, in particular at masses that would correspond to "multicages", 60,61 with spectra similar to those in Figure 12 are observed. The only clusters with similar IR spectra are the (8,12), (8,11), and (7,12) clusters. There are indications that the observed signal at the mass of the (7,12) cluster does not result from excitation of neutral (7,12) and is instead caused by fragmentation of (8,12).…”

“…LIF and REMPI detection can also be used in double (or more) resonance experiments. When one of the photons is in the infrared (IR), spectral information on IR active modes on the electronic ground-state surface of neutral molecules [3][4][5][6][7][8][9][10][11][12] can be obtained. Advances in laser technology now allow performing such experiments at wavelengths up to and beyond 10 µm, although laser fluences decrease rapidly with increasing wavelength.…”

Methane Loss in the Infrared Multiphoton Dissociation of Acetic Acid

“…9 The fluences used in this experiment were on the order of 40 J/cm 2 • A second experiment, using comparable fluences, investigated the decomposition of acetic anhydride to acetic acid which further decomposed to the products ketene, water and methyl radical subsequently detected by VUV photoionization. 10 The formation of CH 3 was attributed to the decomposition of acetyl radical formed in the simple bond rupture reaction (III).…”

10.5-eV photoionization mass spectrometry of aliphatic compounds

“…everal applications of coherent vacuum ultraviolet (VUV) phoroionization have appeared over the past few years [1][2][3][4][5][6]. Although it is possible to generate coherent VUV radiation down to the LiP cutoff at 110 nm [7][8][9][10][11][12], 118 nm (10.5 eV) is perhaps the most convenient wavelength for mass spectrometry.…”