Kautsch Andreas, Koch Markus, Ernst Wolfgang E
Graz University of Technology, Institute of Experimental Physics, NAWI Graz, Petersgasse 16, A-8010 Graz, Austria.
Phys Chem Chem Phys. 2015 May 14;17(18):12310-6. doi: 10.1039/c5cp01009h.
We have investigated photoinduced chemical reaction dynamics of cold, isolated Cr2 molecules in helium nanodroplets (HeN), exploiting the quantum state specific spatial separation of solvated and surface locations on the droplet. The molecules are excited to achieve dissociation to a ground state (a(7)S3) and a metastable state (a(5)S2) atom. State specific spatial separation, in combination with efficient translational cooling to avoid ejection, causes the ground state atom to be solvated inside the droplet while the metastable atom migrates to the surface. A barrier between the two reactants formed by the HeN prevents recombination. We apply a resonance-enhanced multiphoton ionization scheme including the y(5)P°(1,2,3) <-- a(5)S(2) transition of the surface atom as well as a two-laser scheme including the y(7)P°(2,3,4) <-- a(7)S(3) transition of the solvated atom in order to verify the locations and separation of the dissociation products. Furthermore, ionization of the a(5)S2 surface atom triggers solvation followed by geminate recombination with the a(7)S3 atom, which is verified by the detection of Cr2(+) molecular ions. For small Cr clusters, our results indicate that they may be composed of chromium dimers that exhibit the same dissociation behavior.
我们利用液滴上溶剂化位置和表面位置特定的量子态空间分离，研究了氦纳米液滴（HeN）中孤立的冷Cr2分子的光致化学反应动力学。分子被激发以实现解离成基态（a(7)S3）和亚稳态（a(5)S2）原子。特定态的空间分离，结合有效的平动冷却以避免喷射，使得基态原子被溶剂化在液滴内部，而亚稳态原子迁移到表面。由HeN形成的两种反应物之间的势垒阻止了复合。我们应用了一种共振增强多光子电离方案，包括表面原子的y(5)P°(1,2,3) <-- a(5)S(2)跃迁，以及一种双激光方案，包括溶剂化原子的y(7)P°(2,3,4) <-- a(7)S(3)跃迁，以验证解离产物的位置和分离情况。此外，a(5)S2表面原子的电离引发溶剂化，随后与a(7)S3原子发生双分子复合，这通过检测Cr2(+)分子离子得到了验证。对于小的Cr团簇，我们的结果表明它们可能由表现出相同解离行为的铬二聚体组成。
