State selective population of H2(v″=1, J″=1) and D2(v″=1, J″=2) and rotational relaxation in collisions with H2, D2, and He

Abstract

Single rotational states were populated in vibrationally excited hydrogen by stimulated Raman pumping. The population in H2 X 1∑+g(v″=0,1) and D2 X 1∑+g(v″=0,1) was probed state selectively by tunable vacuum ultraviolet (VUV) laser radiation around λ=110 nm, and the fluorescence induced when exciting the hydrogen molecules in the (0–0), (1–0), (2–0), (3–1), and (4–1) Lyman bands of the (B 1∑+u←X 1∑+g) transition monitored. From a comparison of line heights, the stimulated Raman pumping efficiency is estimated to be 30%–50% in the focal volume. Rotational transitions in X 1∑+g(v″=1) were induced in collisions with H2, D2, and He. State-to-state rotational relaxation rates were measured for the (J″=1→J″=3) transition in H2(v″=1) and for the (J″=2→J″=0,4) transitions in D2(v″=1). These rates were found to be generally higher than the corresponding previously determined ones in ground state hydrogen, in qualitative accord with recent theoretical calculations. A comparison with available theoretical state-to-state cross sections shows that the rates obtained with these cross sections are generally lower than the relaxation rates directly measured in this work.

CARS spectroscopy of the NaH2 collision complex: the nature of the Na(32 P)H2 exciplex — ab initio calculations and experimental results

“…Approximately 300 collision [29] or even less [30] are necessary to cause rotational cooling. The resulting number of 1.1012 collisions per cm 3 which will lead to stabilization of the complex lies in the detection sensitivity of the performed CARS experiment.…”

H2-He vibrational line-shape parameters: Measurement and semiclassical calculation

“…Ref. [20]]. Furthermore it would be interesting to compare the present y, value for H2-He to that for the other rare-gas perturbers.…”

“…We have used only Eq. (3) and the detailed balance condition (20) 6.68 (20) nJ WJ J n Jr WJJ& where nJ and n J. are the relative populations of molecules in the Jand J' rotational levels, respectively. In this tem- Fig.…”

Spectroscopy and energetics of the acetylene molecule: dynamical complexity alongside structural simplicity

“…Double-resonance schemes using tunable lasers to monitor coherent Raman excitation of specific molecular rovibrational states were first reported in 1983, with two variants based, respectively, on detection by LIF in D 2 CO vapour [322] and multiphoton ionization (MPI) in NO gas [323]. Subsequent early LIF-detected Raman-UV DR experiments studied glyoxal (C 2 H 2 O 2 ) [324,325], H 2 and D 2 [326], C 2 H 2 [50,52,53,54,57,161,162,[167][168][169][170], C 2 HD and C 2 D 2 [52], and stilbene [327]. Corresponding early MPI-detected Raman-UV DR experiments examined H 2 [328][329][330], benzene and other aromatics [331][332][333][334][335], HCl [336], and N 2 [337].…”