Spin–orbit effects in the formation of the Na–He excimer on the surface of He clusters
Spin–orbit effects in the formation of the Na–He excimer on the surface of He clusters
复制标题
He团簇表面Na-He准分子形成中的自旋轨道效应
DOI：
10.1039/a706108k
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发表时间：
1997
影响因子：
3.4
通讯作者：
G. Scoles
中科院分区：
文献类型：
--
作者：
J. Reho;C. Callegari;J. Higgins;W. Ernst;K. Lehmann;G. Scoles
在这篇文章中，我们描述了反向时间关联单光子计数在大量子团簇上杂质原子和分子的时间分辨光谱中的应用。通过跟踪Na原子在选定的激发和发射波长下的发射随时间的变化，研究了Na原子在He和H2团簇表面的光致动力学。收集从团簇表面激发的Na原子产生的(16980±14 5 cm-1)原子荧光，并立即从团簇表面解吸，得到有限的(约70ps)上升时间和16.3±0.1 ns的衰减时间，相当于Na原子的3P→3S跃迁的已知寿命。由激发后没有立即离开团簇的原子的红光发射的频率分布被证明是由于去吸附的Na~*-He激基复合体，与由可用的从头算Na-He势得到的预测定量地一致。这种准分子的形成可以沿着2Π1/2或2Π3/2激发态表面进行。红色发射上升时间(15800±125 cm-1)的“慢”(700ps)和“快”(约70ps)分量分别被分配给两个形成通道。在孤立Na~*-He的长程从头算对势能中引入自旋-轨道耦合效应，在2Π1/2势能曲线上产生一个小势垒，这与观察到的缓慢激基络合物形成时间有关。
In this paper we describe an application of reversed time-correlated single photon counting to the time-resolved spectroscopy of impurity atoms and molecules bound to large quantum clusters. The photo-induced dynamics of Na atoms on the surface of He and H2 clusters have been studied by following the time dependence of their emission at selected excitation and emission wavelengths. Collection of atomic (16980±145 cm-1) fluorescence arising from Na atoms excited on the cluster surface and immediately desorbed from it yields a finite (ca. 70 ps) rise time and a decay time of 16.3±0.1 ns, equal to the known lifetime of the 3P→3S transition of atomic Na. The frequency distribution of the red emission due to atoms that do not leave the cluster immediately after excitation is shown to be due to a desorbed Na*–He exciplex by obtaining quantitative agreement with predictions derived from available abinitio Na–He potentials. Formation of this excimer can occur along either the 2Π1/2 or 2Π3/2 excited state surface. ‘Slow’ (700 ps) and ‘fast’ (ca. 70 ps) components of the rise time of the red emission (15800±125 cm-1) are assigned, respectively, to the two formation channels. Introducing spin–orbit coupling effects into the long range abinitio pair potential for an isolated Na*–He generates a small barrier on the 2Π1/2 potential curve, which is linked to the observed slow exciplex formation time.