Vibrational relaxation dynamics of SD molecules in As{sub 2}S{sub 3}: Observation of an anomalous isotope effect
- Univ. of Georgia, Athens, GA (United States)
- Stanford Univ., CA (United States); and others
It is generally assumed that the vibrational relaxation of molecular impurities in crystals and glasses mainly depends on the order of the decay process, with lower order processes leading to more rapid relaxation (a behavior that is known under the term {open_quotes}gap-law{close_quotes}). Here we present measurements that contradict this assumption. Using high intensity psec pulses of the Stanford FEL we measured the relaxation rate of the SD vibrational stretch mode (at a frequency of 1800 cm) by applying a pump-probe technique. We find relaxation rates on the order of 2x10{sup 9} sec{sup -1}, which are a factor of 2 lower than those found for the isotope molecule SH (at a frequency of about 2500 cm{sup - 1}) in the same host{sup 1}. We recall that the relaxation of the SD vibrational stretch mode is controlled by a lower order process as compared to the SH molecule, which is due to the smaller number of host vibrational quanta to match the energy of the stretch mode; a fact we have confirmed experimentally by temperature dependent relaxation measurements. Thus our remits are in marked contrast to the so-called {open_quotes}Gap-Law{close_quotes} and emphasize the importance of the molecule - host coupling in the relaxation dynamics.
- Research Organization:
- Brookhaven National Lab., Upton, NY (United States)
- OSTI ID:
- 238872
- Report Number(s):
- BNL--61982-Absts.; CONF-9508156--Absts.; ON: DE96002729; CNN: Grant N00014-94-1-1024
- Country of Publication:
- United States
- Language:
- English
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