Induced Rotation—Translation Spectra of Solutions of H2, HD, and D2 in Liquid Argon

Abstract

Articles you may be interested inA new ab initio intermolecular potential energy surface and predicted rotational spectra of the Ar−H2S complex Theory of depolarized Rayleigh-Brillouin spectra and rotation-translation coupling in molecular liquids and solids Dilute solutions of H2 D2 and HD in liquid argon are studied by examining the 1000-140-cm-1 region of their induced absorption ~pectra. Since the absorption features overlap extensively, an empirical profile analysis is performed. For H2 and D2 several relatively sharp abs~rptions (Llv1/2",,30 cm-I !, which have a Lorentzian line shape and closely correspond to the expected transltlOns of .the freely ro~atmg :olute molecules are observed. The width of these lines appears to be due to uncertamty broadenmg which depends on the time the absorbing solute molecule spends in a particular solvent cavity. Other features, with a 150-cm-1 half-width are fitted with a four-parameter exponential equation and are believed to involve quantized translatio~al energy levels of the solute. The range of translational energy levels, .which is determined by the distribution of solvent cavity sizes, is responsible for their increase? .bandwldths. T~e HD spectrum is unusual in that the rotational selection rules are relaxed and transltlOns corresponding to LlJ = +2, +3, and +4 are observed. Furthermore, all of the rotational absorptio~ fe~ture~ are anomalously broad (LlV1/2"" 50 cm-I ) and their maxima are shifted from the ~as-phase fr:quenc,es III ~n Irregular patte.rn. Because of its asymmetrical mass distribution, rotational motion of HD IS accompamed by a translatIOn of the molecule in its solvent cavity. This rotation-translation interaction has been given quantitative form in a perturbation treatment by Friedmann and Kimel, and the results are consistent with the observed selection rules, frequency shifts, and linewidths in the spectrum of HD in liquid argon.

Collision-Induced Absorption of Hydrogen Deuteride Dissolved in Liquid Neon

“…The intracollisional correlation (IC) between these dipoles distorts the allowed P 1 and R 1 spectral line profiles [4] mostly studied so far in the gas-phase spectra (see, e.g., [5,6], and references therein). Similar effects were observed in the liquid state (neat HD [7] and its solution in Ar [3]), but no theoretical interpretation was advanced.…”

“…This results in an extra torque exerted on the HD molecule from neighboring particles that makes its rotation stronger perturbed compared to symmetric H 2 and D 2 and reveals more detail on the molecular motion dynamics in condensed media. The lack of the center-of-mass inversion symmetry for HD renders active the rotational transitions with J odd [3]. Because of the intramolecular electronic-rotovibrational coupling, HD acquires a small permanent dipole moment M a , comparable in magnitude with the typical values of the collisioninduced dipole moments ab .…”