Research into the relaxation mechanism of the exciton in rare gas solids by the study of desorption induced by electronic transitions (DIET)

通过对电子和光子辐照诱导的稀有气体固体表面解吸的实验研究，探讨了稀有气体固体中激子的动力学方面。我们开发了新的实验系统：(1)用脉管制冷机作为低温恒温器进行固体Kr和Xe的电子激发解吸研究系统；(2)在极高真空条件下进行电子激发解吸研究系统；(3)激光等离子体真空紫外源系统。本研究项目取得的成果总结如下：(1)测定了固体Ne、Ar和Kr表面光诱导解吸的绝对产率。通过在厚膜中的体激子激发，Ne、Ar和Kr的解吸收率分别为1、0.2和0.01-0.1个原子/光子。我们研究了解吸过程中电子激发和光子激发的区别。(3)发现Ne准分子通过空腔喷射机制解吸，其动能约为0.2 eV。解吸的准分子处于最高振动能级，因为解吸比振动松弛发生得快得多。(4)提出了Ne固体体和表面激子弛豫级联的模型图，并通过实验确定了其中的部分分支比。

We have investigated the dynamic aspect of excitons in rare gas solids by the experimental study of the desorption at the surface of rare gas solids induced by electron and photon irradiation.1. We have developed the new experimental systems :(1) system for the electron stimulated desorption study of solid Kr and Xe using a pulse tube refrigerator as a cryostat,(2) system for the desorption induced by electronic excitations study under extremely high vacuum condition,(3) laser plasma vacuum ultra violet source.2. The results achieved in this research project are summarized below.(1) Absolute yields of photo-induced desorption at the surface of solid Ne, Ar, and Kr have been measured. By bulk exciton excitation in a thick film, the desorption yield is 1, 0.2, and 0.01-0.1 atoms/photon for Ne, Ar, and Kr, respectively.(2) We have examined the difference between electron and photon excitations in the desorption processes.(3) We found that Ne excimers were desorbed via the cavity ejection mechanism and had the kinetic enegy of about 0.2 eV.The excimers desorbed were in the highest vibrational level since desorption takes place much faster than vibrational relaxation.(4) The model diagram of the relaxation cascade of excitons in bulk and at surface of solid Ne are proposed and some of the branching ratio in it have experimentally been determined.