First spectroscopic evidence for molecular HCl on a liquid surface with sum frequency generation

Abstract

Sum frequency generation spectroscopy has been used to obtain the vibrational spectrum of HCl on the surface of a liquid. HCl was studied on the surface of 96 wt % ${\mathrm{H}}_{\mathrm{2}}{\mathrm{SO}}_{\mathrm{4}},$ 12 M HCl solution, liquid HCl and glass, of which only liquid HCl produces a resonant signal. Implications for the form of HCl on surfaces and the reactions in the atmosphere are discussed.