HYPERFINE QUANTUM BEATS IN THE 209 NM FLUORESCENCE EXCITATION SPECTRUM OF CYANOGEN

Authors
Citation
N. Hemmi et Ta. Cool, HYPERFINE QUANTUM BEATS IN THE 209 NM FLUORESCENCE EXCITATION SPECTRUM OF CYANOGEN, The Journal of chemical physics, 105(18), 1996, pp. 7964-7975
Citations number
23
Categorie Soggetti
Physics, Atomic, Molecular & Chemical
ISSN journal
00219606
Volume
105
Issue
18
Year of publication
1996
Pages
7964 - 7975
Database
ISI
SICI code
0021-9606(1996)105:18<7964:HQBIT2>2.0.ZU;2-N
Abstract
Singlet-singlet, singlet-triplet, and polarization hyperfine fluoresce nce quantum beats are observed following 209 nm excitation of the 1(1) 4(1) vibronic level of the (A) over tilde((1) Sigma(u)(-)) S-1 singlet state. Singlet-singlet quantum beats arise from S-1-S-0 vibronic coup ling to states of the S-0 manifold lying above the dissociation limit, but isolated from the dissociative continuum by a high barrier to pre dissociation. Measurements of fluorescence lifetimes and quantum beat spectral widths set an upper bound on this predissociation rate of app roximately 10(6) s(-1). The singlet-singlet quantum beats for the N=9 rotational state provide the first example of quantum beats arising fr om superposition states from two separate (I=0 and I=2) nuclear spin s tates. Singlet-triplet quantum beats for N=12 exhibit magnetically ind uced modulations that provide further support for a theoretical model previously used to describe similar modulations for the N=8, 12, and 1 8 rotational states of the 4(1) vibronic level excited at 219 nm. Anal ysis of hyperfine polarization beats, associated with the reversible i nterchange of molecular polarization and nuclear spin polarization, yi elds results in satisfactory agreement with the predictions of the per turbation theory formulation of Fano and Macek. (C) 1996 American Inst itute of Physics.