Femtosecond pump–probe 2D optical Kerr effect spectroscopy of molecular hydrogen crystals

Excitation of rotons in parahydrogen crystals: The laser-induced-molecular-alignment mechanism

“…In particular, the purpose of the paper is to computationally reproduce and explain the recent experimental spectra. 27,29 The present theoretical work provides insights that cannot easily be gained from experiments alone. In connection with the experiments, 27 we also felt the H 2 molecule itself deserved more attention.…”

“…27,29 The present theoretical work provides insights that cannot easily be gained from experiments alone. In connection with the experiments, 27 we also felt the H 2 molecule itself deserved more attention. Therefore, we report a brief gas-phase survey, where the alignment process is worked out much in the same manner as in previous N 2 studies, 12,36-48 elaborating on the differences in the high-B (rotational constant), small-Δα (anisotropy of polarizability) molecule H 2 as compared to the N 2 .…”

“…Theoretical foundations of solid pH 2 are well known 28 and rotational Raman spectra of the solid have also been thoroughly considered. [32][33][34] Although the transverse optical phonon part of the signal is a very prominent feature in the experiments, 27,29,30 it is left out from the discussion by assuming negligible interplay of phonon and roton dynamics. These elementary excitations have a tenfold energy mismatch and a fivefold difference in dephasing time.…”

“…26,27 In the presence of one J = 2 roton in solid pH 2 , there is one molecule in the J = 2 rather than in J = 0 state. The states in this J = 2 band form a traveling rotational excitation, i.e., the total angular momentum is located at a different molecule at different times.…”

“…27 The coherent oscillation of ca. 94 fs period originates from the J = 2 ← 0 excitation S 0 (0) that can be categorized as a creation of delocalized rotons.…”