@article{11645,
  author = {Timothy Large and David Nesbitt},
  title = {Quantum State and Doppler-Resolved Scattering of Thermal/Hyperthermal DCl at the Gas–Liquid Interface: Support for a Simple “Lever Arm” Model of the Energy-Transfer Dynamics},
  abstract = {Supersonically cooled deuterium chloride (10 K, DCl(J ≈ 0, 1)) has been scattered from the gas–liquid interface under thermal (Einc = 1.5(1) kcal/mol) and hyperthermal (Einc = 11.5(5) kcal/mol) conditions for a series of prototypical liquids (perfluoropolyether (PFPE), squalane, and glycerol), with the final DCl quantum states detected with narrow-band IR laser absorption methods to achieve rotational (J) and transverse Doppler (vy) resolutions. First of all, we see direct evidence for both trapping desorption (TD) and impulsive scattering (IS) components in the DCl distributions, with both TD rotational and transverse velocity components fully equilibrated with the liquid (TS ≈ Trot ≈ TDopp). Second, high-resolution laser dopplermetry on the IS component reveals quite efficient transfer from Einc into out-of-plane scattering of the DCl, in contrast with the notably inefficient channeling of the collision energy into end-over-end rotation. Third, though the rotational excitation efficiency is low, the impulsively scattered DCl(J) exhibits much hotter rotational distributions from gas–liquid interfaces dominated by polar (CF) versus nonpolar (CH) bonds (i.e., Trot(PFPE) ≫ Trot(squalene) ≈ Trot(glycerol)). We interpret our results in terms of a simple kinematic “lever arm” collision model, by which the angle of the DCl striking the surface influences the torque delivered by changing the effective lever arm and thereby enhancing or diminishing rotational excitation. Finally, we extend this simple model to more realistic gas–liquid interfaces with surface roughness due to thermally activated capillary waves, which smooths out any sharp rotational structure. Of particular note is that such an averaging predicts a surprisingly Boltzmann-like distribution of final quantum states characteristic of a rotational “temperature”, which is in agreement with many previous gas–liquid scattering studies with internal quantum state resolution.},
  year = {2019},
  journal = {The Journal of Physical Chemistry C},
  volume = {123},
  number = {6},
  pages = {3449-3460},
  month = {2019-01},
  url = {https://doi.org/10.1021/acs.jpcc.8b07359},
  doi = {10.1021/acs.jpcc.8b07359},
}