Model calculation on the pump-probe measurement of ultrafast electronic population decay in polyatomic molecules
✍ Scribed by W. Domcke; H. Köppel
- Publisher
- Elsevier Science
- Year
- 1987
- Tongue
- English
- Weight
- 763 KB
- Volume
- 140
- Category
- Article
- ISSN
- 0009-2614
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✦ Synopsis
We consider the common situation of strong vibronic coupling of an optically bright (in absorption from the ground state) excited electronic state to a lower-lying dark electronic state in a polyatomic molecule. It is shown that for sufficiently short pump and probe laser pulses a time-resolved experiment measures the total time-dependent population probability P(t) of the bright state. For a realistic model problem (representing the three lowest electronic states of the benzene cation) a conical intersection of the potential energy surfaces of the bright and the dark state causes an ultrafast initial decay of P( t) on a femtosecond time scale, followed by quasiperiodic recurrences. These recurrences show up as femtosecond quantum beats in the time-resolved pump-probe signal. The beating frequency is related to the vibrational frequency of the dominant accepting mode of the system.