First measurements of internal quantum-state distributions for nitric oxide (NO) evaporating from liquid benzyl alcohol are presented over a broad range of temperatures, performed by liquid-microjet techniques in an essentially collision-free regime, with rotational/spin–orbit populations in the 2 Π 1/2,3/2 manifolds measured by laser-induced fluorescence. The observed rotational distributions exhibit highly linear (i.e., thermal) Boltzmann plots but notably reflect rotational temperatures ( T rot ) as much as 30 K lower than the liquid temperature ( T jet ). A comparable lack of equilibrium behavior is also noted in the electronic degrees of freedom but with populations corresponding to spin–orbit temperatures ( T SO ) consistently higher than T rot by ∼15 K. These results unambiguously demonstrate evaporation into a non-equilibrium distribution, which, by detailed-balance considerations, predict quantum-state-dependent sticking coefficients for incident collisions of NO at the gas–liquid interface. Comparison and parallels with previous experimental studies of NO thermal desorption and molecular-beam scattering in other systems are discussed, which suggests the emergence of a self-consistent picture for the non-equilibrium dynamics.
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Rotational state-to-state transition rate coefficients for H 2 O + H 2 O collisions at nonequilibrium conditions
- Award ID(s):
- 2009253
- PAR ID:
- 10558074
- Publisher / Repository:
- MNRAS
- Date Published:
- Journal Name:
- Astronomy & Astrophysics
- Volume:
- 688
- ISSN:
- 0004-6361
- Page Range / eLocation ID:
- A208
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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