Mapping the temperature-dependent and network site-specific onset of spectral diffusion at the surface of a water cluster cage

• DOI: 10.1073/pnas.2017150117
• Publication Date: 2020-10-06T20:30:20Z
• Authors: Nan Yang; Sean C. Edington; Tae Hoon Choi; Elva V. Henderson; Joseph P. Heindel; Sotiris S. Xantheas; Kenneth D. Jordan; Mark A. Johnson
• Keywords: Millisecond; Envelope (radar); Kinetic isotope effect; Cage effect; Cage

Significance Water’s vibrational spectrum is dynamic: The OH oscillator frequency changes spontaneously within a diffuse envelope on an ultrafast timescale. Here, we explore the mechanics that drive this “spectral diffusion” at molecular level by following time-dependent of single oscillators, each embedded in cage 20 deuterated water molecules, as function temperature. These cages are isolated gas phase and incorporate single, isotopically labeled group can occupy many spectroscopically distinct sites. rates spontaneous change reflect pathways for migration isotopic label among these sites, which occurs remarkably long (approximately millisecond) timescale onset large-amplitude motion near 100 K.