| 论文简介 |
Molecular dynamics simulations for ultrafast processes in molecules have been attracted more and more attentions these years. Semiclassical simulation, whose efficiency is between classical simulation and quantum simulation, is an effective method to describe many ultrafast processes in molecules and materials. In this article, we briefly review some recent studies by the present authors using our method of semiclassical electron-radiationion
dynamics (SERID). In particular, Jiang et al. reported reaction mechanism of the trans-to-cis photoisomerization of stilbene induced by a femtosecond-scale laser pulse. The detailed results imply that basic mechanism of trans-to-cis isomerization is essentially the same as that for cis-to-trans photoisomerization, although the time scale is longer, because bond rotation is not induced directly. Jiang et al. also predicted that photocyclization of trans-stilbene to 4a,4b-dihydrophenanthrene can be achieved under a femtosecond-scale laser pulse, with an excited cis conformer as intermediate product. For a bridged azobenzene 5,6-dihydrodibenzo[c, g][1, 2] diazocine (B-Ab), Jiang et al. found that quantum yield of its trans-to-cis isomerization is much larger than that of azobenzene. Lifetime of the S1 excited state for trans-B-Ab (about 30 fs) is much shorter than that of transazobenzene.
The complete trans-to-cis isomerization for B-Ab and azobenzene have approximately the same
timescales: Although the bridging feature in trans-B-Ab does not hinder rotation around the NN bond on the S1 excited state, it makes twisting of the two phenyl rings around the CN much slower on its ground state. Zhou et al. and Jiang et al. respectively, determined the optimal duration and optimal timing for a series of femtosecond-scale laser pulses to excite a specific vibrational mode in a general chemical system. A set of
such modes can be used as a “fingerprint” for characterizing a particular molecule or a complex in a solid. One can therefore envision many applications, ranging from fundamental studies to detection of chemical or biological agents. |
(创新港)
