Abstract
Insights into energy flow dynamics at ice surfaces are essential for understanding chemical dynamics relevant to atmospheric and geographical sciences. Here, employing ultrafast surface-specific spectroscopy, we report the interfacial vibrational dynamics of ice Ih. A comparison to liquid water surfaces reveals accelerated vibrational energy relaxation and dissipation at the ice surface for hydrogen-bonded OH groups. In contrast, free-OH groups sticking into the vapor phase exhibit substantially slower vibrational dynamics on ice. The acceleration and deceleration of vibrational dynamics of these different OH groups at the ice surface are attributed to enhanced intermolecular coupling and reduced rotational mobility, respectively. Our results highlight the unique properties of free-OH groups on ice, putatively linked to the high catalytic activities of ice surfaces.
Highlights
Insights into energy flow dynamics at ice surfaces are essential for understanding chemical dynamics relevant to atmospheric and geographical sciences
Solar photon-induced vibrational overtone pumping induces photodissociation of atmospherically relevant compounds[1] like HNO4,2 HO2NO2,3 H2SO4,4 etc. When such reagents are adsorbed on omnipresent aqueous or ice surfaces, their vibrational modes can couple to water vibrational modes, e.g., through energy transfer,[5] thereby influencing the reaction pathway
Many studies have reported on vibrational dynamics of bulk ice[12−15] and water[16−21] and interfacial water.[11,22−25] Here, we compare the vibrational dynamics of surface OH groups on singlecrystalline hexagonal ice oriented to the basal plane with those on water
Summary
Insights into energy flow dynamics at ice surfaces are essential for understanding chemical dynamics relevant to atmospheric and geographical sciences. The Supporting Information (SI) contains data for ice excited at 3310 cm−1 and water at both excitation frequencies.
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