In:
The Journal of Chemical Physics, AIP Publishing, Vol. 125, No. 5 ( 2006-08-07)
Abstract:
We present a complete characterization, based on femtosecond pump-probe spectroscopy and molecular dynamics simulations, of the ultrafast dynamics of electronic bubble formation in solid parahydrogen upon impulsive excitation of impurity-doped sites, which correlate with the lowest Rydberg state of the NO impurity. The high temporal resolution of the experiment allows us to identify three time scales in the structural dynamics. A first ultrafast expansion ( & lt;150fs), associated with the release of ∼80% of the excess energy available to the system after excitation, is accompanied by a transient narrowing of the spatial distribution of the first shell of H2 molecules around the impurity. In a subsequent stage (up to ∼800fs), the cavity expansion slows down, and energy starts to flow irreversibly into the crystal. Finally, the lattice undergoes a slow structural reorganization at the impurity site (5–10ps). A weak low-frequency recurrence, probably associated with an elastic response of the crystal, is observed at ∼10ps. The absence of polarization dependence indicates that the dynamics is largely dominated by translational (radial) motions of the molecules surrounding NO and not by the rotational motion of the impurity. Molecular dynamics simulations with temperature corrections, to mimic zero-point fluctuations, fully support the experimental results and show that the bubble model is suited to describe the dynamics of the system. It appears that the response of the medium around the impurity at short times is typical of a liquid solvent rather than that of a solid.
Type of Medium:
Online Resource
ISSN:
0021-9606
,
1089-7690
Language:
English
Publisher:
AIP Publishing
Publication Date:
2006
detail.hit.zdb_id:
3113-6
detail.hit.zdb_id:
1473050-9
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