Bragg Arthur E, Verlet Jan R R, Kammrath Aster, Cheshnovsky Ori, Neumark Daniel M
Department of Chemistry, University of California, Berkeley, CA 94720, USA.
J Chem Phys. 2005 Feb 1;122(5):54314. doi: 10.1063/1.1828042.
Time-resolved photoelectron imaging has been used to study the relaxation dynamics of small Hg(n) (-) clusters (n=7-13,15,18) following intraband electronic excitation at 1250 nm (1.0 eV). This study furthers our previous investigation of single electron, intraband relaxation dynamics in Hg(n) (-) clusters at 790 nm by exploring the dynamics of smaller clusters (n=7-10), as well as those of larger clusters (n=11-13,15,18) at a lower excitation energy. We measure relaxation time scales of 2-9 ps, two to three times faster than seen previously after 790 nm excitation of Hg(n) (-), n=11-18. These results, along with size-dependent trends in the absorption cross-section and photoelectron angular distribution anisotropy, suggest significant evolution of the cluster anion electronic structure in the size range studied here. Furthermore, the smallest clusters studied here exhibit 35-45 cm(-1) oscillations in pump-probe signal at earliest temporal delays that are interpreted as early coherent nuclear motion on the excited potential energy surfaces of these clusters. Evidence for evaporation of one or two Hg atoms is seen on a time scale of tens of picoseconds.
时间分辨光电子成像已被用于研究小汞团簇Hg(n)(-)（n = 7 - 13、15、18）在1250 nm（1.0 eV）带内电子激发后的弛豫动力学。本研究通过探索较小团簇（n = 7 - 10）以及较大团簇（n = 11 - 13、15、18）在较低激发能量下的动力学，进一步拓展了我们之前对汞团簇Hg(n)(-)在790 nm处单电子带内弛豫动力学的研究。我们测量到弛豫时间尺度为2 - 9皮秒，比之前在790 nm激发Hg(n)(-)（n = 11 - 18）后观察到的快两到三倍。这些结果，连同吸收截面和光电子角分布各向异性的尺寸依赖趋势，表明在此研究的尺寸范围内团簇阴离子电子结构有显著演化。此外，这里研究的最小团簇在最早的时间延迟时泵浦 - 探测信号中表现出35 - 45厘米(-1)的振荡，这被解释为这些团簇激发势能面上的早期相干核运动。在几十皮秒的时间尺度上可以看到一个或两个汞原子蒸发的证据。
