Vibrational spectroscopy of cluster ions: Two novel methods

Conference · Wed Jul 01 00:00:00 EDT 1987

OSTI ID:5926714

Yeh, L I; Okumura, M; Myers, J D; Lee, Y T

Two sensitive techniques are discussed for obtaining vibrational spectra of cluster ions. The first approach is to attach a H/sub 2/ molecule to the hydrated hydronium ions. Because the original goal was to study the hydrated hydronium ions, the attached H/sub 2/ is hoped to have only a small effect on the spectrum. After an O-H stretch of the cluster ion has been excited, it vibrationally predissociates, losing the H/sub 2/. By monitoring the dissociation product as a function of laser frequency, the absorption spectra of these H/sub 3/O/sup +/ . (H/sub 2/O)/sub n/ . H/sub 2/ (n = 1,2,3) ions have been found. The second approach is to detect the vibrationally excited H/sub 3/O/sup +/ . (H/sub 2/O)/sub n/ (n = 1,2,3) ions using an infrared multiphoton dissociation process. The procedure is to first excite from v = 0 to v = 1 in the O-H stretch using a tunable ir laser. We then make use of the fact that the density of states near v = 0 and v = 1 are very different, and the vibrationally excited ionic clusters, which contain many low frequency vibrations, are likely to be in the quasicontinuum region for the sequential excitation by a fixed frequency laser. This means that one can distinguish between ground state and vibrationally excited H/sub 3/O/sup +/ . (H/sub 2/O)/sub n/ by using a multiphoton dissociation (MPD) process to selectively dissociate the latter using a CO/sub 2/ laser. Once again, we monitor the dissociation product ion signal as a function of the excitation frequency of the first laser to get the absorption spectra of the H/sub 3/O/sup +/ . (H/sub 2/O)/sub n/ ions. 5 refs.

• Research Organization: Lawrence Berkeley Lab., CA (USA)
• DOE Contract Number: AC03-76SF00098
• OSTI ID: 5926714
• Report Number(s): LBL-23842; CONF-8704211-1; ON: DE88000617
• Conference Information: CAMS/NCR workshop on molecular and cluster beam science, Washington, DC, USA, 24 Apr 1987
• Country of Publication: United States
• Language: English

Related Subjects

640302* -- Atomic
Molecular & Chemical Physics-- Atomic & Molecular Properties & Theory
74 ATOMIC AND MOLECULAR PHYSICS
CHARGED PARTICLES
DISSOCIATION
DYE LASERS
EMISSION SPECTROSCOPY
ENERGY LEVELS
EXCITED STATES
HYDROGEN COMPOUNDS
HYDROGEN IONS
HYDROXIDES
ION PAIRS
IONS
LASERS
LIQUID LASERS
MASS SPECTROMETERS
MEASURING INSTRUMENTS
MULTI-PHOTON PROCESSES
OXYGEN COMPOUNDS
SPECTROMETERS
SPECTROSCOPY
VIBRATIONAL STATES