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F. Fernández-Alonso, B.D. Bean, J.D. Ayers, A.W. Pomerantz, R.N. Zare
New Scheme for Measuring the Angular Momentum Spatial Anisotropy of Vibrationally Excited H2 via the I 1Πg State
We report the spectroscopic detection of vibrationally excited molecular hydrogen using 2+1 resonantly enhanced multiphoton ionization (REMPI) via the I 1Πg (vī = 0) - X 1∑ +g (v" = 3) band ca. 198 nm. Vibrationally excited H2 was produced by passing room-temperature hydrogen over a hot ion gauge filament in a high-vacuum chamber. The internal energy distributions were characterized spectroscopically by use of the EF 1∑ +g -X 1∑ +g 2+1 REMPI detection scheme. We have identified band origins for the S, Q, R, and P rotational branches of the I-X (0,3) band, as well as isolated lines corresponding to two-photon transitions into other nearby H2 gerade states, including EF 1∑ +g (vī = 2, 3, 4), GK 1∑ +g(vī = 1), and J 1Δ g (vī = 0). We propose the I-X transition as a suitable candidate for the determination of the rotational anisotropy of vibrationally excited ground-state H2 molecules. We support this contention with a calculation of the line strength moments and sensitivities to the second- (quadrupolar) and fourth-rank (hexadecapolar) moments of the rotational angular momentum distributions, which is compared against the well-established Q-branch members of the EF 1∑ +g -X 1∑ +g two-photon transition.
Zeitschrift für Physikalische Chemie, Oldenbourg Wissenschaftsverlag
Print ISSN: 0942-9352
Volume: 214, 09/2000
Pages: 1167