ULTRAFAST PHOTODISSOCIATION OF I-3 - COHERENT PHOTOCHEMISTRY IN SOLUTION
ULTRAFAST PHOTODISSOCIATION OF I-3 - COHERENT PHOTOCHEMISTRY IN SOLUTION
复制标题
DOI：
10.1063/1.465066
复制
发表时间：
1993-03-15
影响因子：
4.4
通讯作者：
RUHMAN, S
中科院分区：
文献类型：
--
作者：
BANIN, U;RUHMAN, S
本文报道了用飞秒时间分辨瞬态透射实验对乙醇溶液中I3-的紫外光解进行了全面的研究。我们解释我们的结果表明，在高概率下，光激发导致在300fs内直接形成二碘离子，这些离子是相干振动的。通过我们的实验，我们已经能够确定碎片离子的振动减相、振动弛豫和重定向的时间尺度分别为400fs、4ps和5ps。620nm和880nm的传输信号，在已知I2-吸收的λ (max)之上和之下，以完全相反的相位振荡。这一结果和其他结果表明，通过振荡我们观察到I2-光碎片的相干振动。为了表征复合的时间尺度，我们进行了紫外瞬态透射实验。初步结果表明，复合发生在几个时间尺度上。在I3-基态的振动弛豫中，初始复合有一个快速分量。I3-光激发的脉冲性质在基态三碘化物居群中引起相干对称伸缩振动。最后，直接探测到的大量动态变量使我们能够以前所未有的细节记录这一反应的年表。我们直接观察到这个反应的一个新的和潜在的信息动力学变量——光解后碎片振动的绝对相位。
We report a comprehensive study of the UV photolysis of I3- in ethanol solution, using femtosecond time resolved transient transmission experiments. We interpret our results to indicate that with high probability, photoexcitation leads to direct formation of di-iodide ions within 300 fs, which are vibrating coherently. Through our experiments we have been able to determine that the time scales for vibrational dephasing, vibrational relaxation, and reorientation of the fragment ions are 400 fs, 4 ps, and 5 ps, respectively. Transmission signals at 620 nm and at 880 nm, which are above and below the lambda(max) of the known absorption of I2-, oscillate at a precisely opposite phase. This and other results presented indicate that through the oscillations we are observing coherent vibration of the I2- photofragment. UV transient transmission experiments have been conducted in order to characterize the time scales for recombination. Preliminary results show that recombination takes place on several time scales. A fast component is assigned to primary recombination, followed by vibrational relaxation on the ground state of I3-. The impulsive nature of the I3- photoexcitation induces coherent symmetric stretching vibration in the ground state tri-iodide population. Finally, the large number of dynamical variables probed directly allows us to record the chronology of this reaction with unprecedented detail. We directly observe a new and potentially informative dynamical variable for this reaction-the absolute phase of fragment vibrations following the photodissociation.