Rotational Dynamics of the Methyl Radical in Superfluid 4He Nanodroplets

Morrison, Alexander M.; Raston, Paul L.; Douberly, Gary E.

doi:10.1021/jp310083j

Rotational Dynamics of the Methyl Radical in Superfluid ⁴He Nanodroplets

Journal Article · Fri Dec 07 00:00:00 EST 2012 · Journal of Physical Chemistry. A, Molecules, Spectroscopy, Kinetics, Environment, and General Theory

DOI:https://doi.org/10.1021/jp310083j· OSTI ID:1409048

Morrison, Alexander M. ^[1]; Raston, Paul L. ^[2]; ^[2]

Univ. of Georgia, Athens, GA (United States); University of Georgia, Athens, GA
Univ. of Georgia, Athens, GA (United States)

Here, we report the ro-vibrational spectrum of the ν₃(e') band of the methyl radical (CH₃) solvated in superfluid ⁴He nanodroplets. Five allowed transitions produce population in the N_K = 0₀, 1₁, 1₀, 2₂ and 2₀ rotational levels. The observed transitions exhibit variable Lorentzian line shapes, consistent with state specific homogeneous broadening effects. Population relaxation of the 00 and 11 levels is only allowed through vibrationally inelastic decay channels, and the ^PP₁(1) and ^RR₀(0) transitions accessing these levels have 4.12(1) and 4.66(1) GHz full-width at half-maximum line widths, respectively. The line widths of the ^PR₁(1) and ^RR₁(1) transitions are comparatively broader (8.6(1) and 57.0(6) GHz, respectively), consistent with rotational relaxation of the 2₀ and 2₂ levels within the vibrationally excited manifold. The nuclear spin symmetry allowed rotational relaxation channel for the excited 1₀ level has an energy difference similar to those associated with the 2₀ and 2₂ levels. However, the ^PQ₁(1) transition that accesses the 1₀ level is 2.3 and 15.1 times narrower than the ^PR₁(1) and ^RR₁(1) lines, respectively. The relative line widths of these transitions are rationalized in terms of the anisotropy in the He-CH₃ potential energy surface, which couples the molecule rotation to the collective modes of the droplet.

View Accepted Manuscript (DOE)

Research Organization:: Univ. of Georgia Research Foundation, Athens, GA (United States)

Sponsoring Organization:: USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22). Chemical Sciences, Geosciences & Biosciences Division

Grant/Contract Number:: SC0008086

OSTI ID:: 1409048

Journal Information:: Journal of Physical Chemistry. A, Molecules, Spectroscopy, Kinetics, Environment, and General Theory, Journal Name: Journal of Physical Chemistry. A, Molecules, Spectroscopy, Kinetics, Environment, and General Theory Journal Issue: 46 Vol. 117; ISSN 1089-5639

Publisher:: American Chemical SocietyCopyright Statement

Country of Publication:: United States

Language:: English

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