Quantum-State-Resolved Scattering of NO(2Π1/2) from Hot Molten Au(liq): On the Role of Thermal Electron–Hole Pairs in Vibrational Excitation Dynamics
Energy transfer at the gas–molten Au interface is investigated in quantum-state-resolved molecular beam experiments of supersonically cooled NO scattered from liquid Au (TS = 1400(40) K) and detected via laser-induced fluorescence. Inelastic dynamics at the gas–Au(liq) interface is evidenced through collisional excitation of both (i) nonadiabatic electronic/spin–orbit and (ii) rovibrational degrees of freedom of NO at near thermal (2.0(7) kcal/mol) and hyperthermal (20(2) kcal/mol) collision energies. The studies represent first molecular beam scattering experiments from molten Au, as well as the first observations of vibrational excitation by scattering at the gas–liquid metal interface. In the vibrationally elastic NO(v = 0 ← 0) channel, spin–orbit and rotational excitation are found to increase significantly with collision energy. However, excitation in these degrees of freedom are largely energy-independent for the vibrationally inelastic (v = 1 ← 0) channel. One simple physical interpretation of these results is that excitation of NO(v = 1) arises from thermally populated electron–hole pair excitations in the metal itself. Finally, comparisons are made between scattering dynamics from single-crystal Au(111) and molten gold, whereby rotational and vibrational excitation of scattered NO appear to follow a smooth trend as a function of Au surface temperature across the crystal-to-liquid phase transition.
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The Journal of Physical Chemistry C
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