Discharge Pumped Rare-Gas Excimer Lasers in Vacuum Ultraviolet Spectral Region

稀有气体准分子激光器是极具吸引力的真空紫外光源，在其光谱中心附近具有高功率可调输出。然而，它们的振荡只能通过电子束抽运来实现。电子束抽运的稀有气体准分子激光器由于其低重复操作而在实际应用中存在困难。因此，稀有气体准分子被认为是由一个激发的稀有气体原子与两个基态原子的三体碰撞产生的。在这种情况下，高压操作是有利的，因为稀有气体准分子的形成速率与气体压力的平方成正比。众所周知，在高压气体中均匀辉光放电是很难建立的。我们提出了一种新的稀有气体准分子的形成概念，即稀有气体准分子是在膨胀射流放电中由稀有气体团簇形成的。实验证实，在放电电子的激发下，Xe团簇可以形成更多的准分子。用TOF光谱仪对Xe团簇进行三光子电离，测量了其大小分布。在3atm膨胀射流下游3mm处测得Xe二聚体的密度为10^<17>cm^<-3>。到8 atm。经济停滞的压力。测得Xe准分子密度为10^9cm^<-3>，团簇密度为10^<17>cm^<-3>。这些极低效率的准分子形成的簇被认为是不合适的放电条件。在直流电荷中，^3SIGMA准分子态的辐射跃迁占主导地位，因此没有观察到受激辐射，因为^3SIGMA态的受激辐射截面比^1SIGMA态小3个数量级。因此，人们认为快速脉冲放电对于获得高激光增益是必不可少的。指出利用^3SIGMA跃迁的准分子辐射可以制备高效真空紫外光是非常重要的。在未来的电子能量依赖的激发截面的稀有气体准分子簇将被测量，以得出有效的放电条件。少

Rare gas excimer lasers are atractive vacuum ultraviolet sources with high power tunable output around the center of their spectra. However, their oscillation have been obtained only by electron beam pumping. The electron beam pumped rare gas excimer lasers have difficulties for applications because of their low repitition operation. It, therefore, has been desired the rare gas excimers were considered to produce by three body collisions of an excited rare gas atom with two of ground state atoms. In this case a high pressure operation is favorable, because a formation rate of raer gas excimers is proportional to the square of the gas pressure. It is well known that uniform glow discharges in the high pressure gas are very difficult to establish. We have proposed a new concept of formation of the rare gas excimers in which the rare gas excimers were formed from rare gas clusters in an expanding jet discharge.In this project it has been experimentary confirmed that Xe excimers were forme … More d from the Xe clusters excited by discharge electrons. Distributions of sizes of the Xe clusters were measured with a TOF spectrometer by three photon ionization of the clusters. Densities of the Xe dimers were measured to be 10^<17>cm^<-3> at 3mm down stream of the expanding jet with 3atm.to 8atm.of staggnation pressures. Densities of Xe excimers were measured to be 10^9cm^<-3>, the densities of the clusters were 10^<17>cm^<-3> though. These very low efficiency of excimer formation from the clusters is considered to be unsuitable discharge conditions.In DC sischarges radiative transitions from the ^3SIGMA excimer state were predominant, stimulated emissions, therefore, were not observed because the stimulated emission cross section of ^3SIGMA state was three orders smaller than that of ^1SIGMA state. As a result it is considered that fast pulsed discharges should be essential for obtaining a high laser gain.It is very important to point out that an efficinet vacuum ultraviolet lamp can be produced using the excimer radiation by the ^3SIGMA transitions.In future electron energy dependences of the excitation cross sections of rare gas excimers from the clusters will be measured in order to conclude efficient discharge conditions. Less