Akopyan Mikhail E, Lukashov Sergey S, Poretsky Sergey A, Pravilov Anatoly M, Torgashkova Anna S, Buchachenko Alexei A, Suleimanov Yury V
V. A. Fock Institute of Physics, Physical Faculty, St. Petersburg State University, Ul'yanovskaya 1, Staryj Peterhof, 198504 St. Petersburg, Russia.
J Chem Phys. 2008 Sep 21;129(11):114309. doi: 10.1063/1.2978170.
Nonadiabatic transitions among the first-tier ion-pair states of the iodine molecule in collisions with CF(4) and SF(6) partners are investigated by detecting the luminescence following the optical-optical double resonance excitation of the E0(g) (+)-state to the vibrational levels v(E)=8, 13, and 19. Total and partial rate constants, as well as vibrational product state distributions, are determined. It is found that electronic energy transfer in all channels is predominantly assisted by excitation of the dipole-allowed nu(3) and nu(4) modes of the partner. The measurements are accompanied by quantum scattering calculations that implement a close coupling treatment for the electronic and vibrational degrees of freedom and combine diatomics-in-molecule and long-range models for diabatic potential energy surfaces and coupling matrix elements. The analysis of experimental and theoretical data shows that the transitions without excitation of the partner are due to short-range couplings, whereas the vibrational excitation of the partner in the D0(u) (+) channel originates from the long-range coupling of two transition dipole moments: electronic of the iodine molecule and vibrational of the partner. Unexpectedly efficient excitations of the partner in the other ion-pair states, which are not coupled to the initial E0(g) (+)-state by the transition dipole, are interpreted within the postcollision mechanism. Qualitatively, this implies that during a single collision the long-range nonadiabatic transitions to D, nu(3) and D, nu(4) channels are followed by secondary short-range transitions without changing the state of the partner.
通过检测碘分子的E0(g) (+)态到振动能级v(E)=8、13和19的光-光双共振激发后的发光，研究了碘分子与CF(4)和SF(6)伙伴碰撞时第一级离子对态之间的非绝热跃迁。确定了总速率常数和部分速率常数以及振动产物态分布。结果发现，所有通道中的电子能量转移主要是由伙伴的偶极允许的ν(3)和ν(4)模式的激发所辅助的。测量过程伴随着量子散射计算，该计算对电子和振动自由度进行了紧密耦合处理，并将分子内双原子模型和长程模型结合用于非绝热势能面和耦合矩阵元。对实验和理论数据的分析表明，未激发伙伴的跃迁是由于短程耦合引起的，而在D0(u) (+)通道中伙伴的振动激发源于两个跃迁偶极矩的长程耦合：碘分子的电子偶极矩和伙伴的振动偶极矩。在碰撞后机制中解释了在其他离子对态中伙伴意外高效的激发，这些态通过跃迁偶极矩与初始E0(g) (+)态不耦合。定性地说，这意味着在单次碰撞期间，向D, ν(3)和D, ν(4)通道的长程非绝热跃迁之后是二次短程跃迁，而伙伴的状态不变。
