Inelastic Scattering of CN Radicals at the Gas-Liquid Interface Probed by Frequency-Modulated Absorption Spectroscopy

Research output: Contribution to journalArticle

Abstract

We describe the results of the first application of frequency-modulated (FM) absorption spectroscopy to molecular scattering dynamics at a gas-liquid interface. A pulsed direct-current electric discharge of a supersonic expansion of BrCN seeded in He was used to generate a pulsed molecular beam of rotationally cold CN(X2Σ+) radicals, with a mean laboratory-frame kinetic energy of 43.5 kJ mol-1. The molecular beam was directed at normal incidence onto a continually refreshed perfluoropolyether liquid surface. FM absorption spectroscopy on the CN(A2Π-X2Σ+) (2,0) band was used to measure Doppler lineshapes for individual CN rotational states as a function of time after the DC discharge pulse. This enabled the characterization of both the incident molecular beam and inelastically surface-scattered CN rotational and translational energy distributions. The surface-scattered CN rotational distribution is well-characterized by a single temperature of 850 ± 130 K. The translational distributions perpendicular to the surface normal are non-Maxwellian, and are substantially superthermal. We interpret these observations as the result of impulsive scattering being the dominant mechanism, similar to our previous independent measurements of OD inelastic scattering at liquid surfaces. Within the current limitations of signal-to-noise, no clear evidence for a discrete component from thermal desorption is observed, in contrast to previous literature measurements of NO and CO2 scattering at perfluoropolyether surfaces.
Original languageEnglish
Pages (from-to)16439-16448
Number of pages10
JournalJournal of Physical Chemistry C
Volume124
Issue number30
Early online date7 Jul 2020
DOIs
Publication statusPublished - 30 Jul 2020

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry

Fingerprint Dive into the research topics of 'Inelastic Scattering of CN Radicals at the Gas-Liquid Interface Probed by Frequency-Modulated Absorption Spectroscopy'. Together they form a unique fingerprint.

  • Cite this