Accession Number : ADP008256

Title :   Antihole Formation in Intramolecular Rotational Tunnel Systems,

Corporate Author : MAINZ UNIV (GERMANY F R)

Personal Author(s) : Gradl, G. ; Feis, A. ; Friedrich, J.

Report Date : 22 MAY 1992

Pagination or Media Count : 4

Abstract : Hole burning in mixed crystals containing methyl groups can be used to determine the difference of the rotational tunnel splitting of the methyl groups in the ground and excited electronic state of the guest probe. Two mechanisms were suggested: If the photo-transformation of the probe is photochemical in nature, the difference in tunnel splitting shows up in the side hole pattern which appears upon thermal relaxation of the bleached ground state levels through spin conversion processes. On the other hand, if the photo-transformation is purely photophysical in nature, the nuclear spin conversion occurs most probably in the excited triplet state and the tunnel splitting is reflected in the appearance of antiholes. In this paper, we show that for dimethyl-s-tetrazine as a diluted guest in a n-octane host, the difference in the methyl tunnel splitting leads to the formation of two very sharp, perfectly Lorentzian antiholes. 'Mis splitting is 20 times as large as that for dimethyl-s-tetrazine in durene measured by Borezyskowski et al. /l/. The absolute magnitude of the tunnel splitting in the ground state is comparable to kT leading to an intensity difference of the two antiholes from which the absolute magnitude of the tunnel splitting in the ground as well as in the electronically excited state can be determined.

Descriptors :   *MOLECULAR SPECTROSCOPY, CONVERSION, CRYSTALS, ELECTRONIC STATES, ELECTRONICS, GROUND STATE, INTENSITY, NUCLEAR SPINS, PROBES, RELAXATION, SPLITTING, TUNNELS, FREQUENCY, OPTICAL PROPERTIES.

Subject Categories : Atomic and Molecular Physics and Spectroscopy
      Crystallography

Distribution Statement : APPROVED FOR PUBLIC RELEASE