钠与惰性气体及烷烃准分子对吸收系数的实验与理论评价

准分子泵浦钠金属激光器(XPNaL)在钠导星中有着极为重要的应用。但是,传统的准分子对,例如Na-He和Na-Ar等对相对于泵浦源的吸收系数很小。本文对Na-Ar、Na-Xe、Na-CH₄、Na-C₂H₆四个体系进行了研究,从荧光实验和结合能的高精度量化理论计算两方面来探究比较好的准分子对。实验结果表明:这四个准分子对体系的荧光强度曲线峰面积比为1.0 : 6.4 : 4.9 : 10.4。同时,通过CCSD(T)手段和基组外推法对Na-Ar、Na-Xe、Na-CH₄和Na-C₂H₆准分子对的结合能计算结果分别为52.8、124.5、117.7和150.0cm^-1。因此,可以推断量化计算与实验结果能够较好地符合。随后, Na-C₂H₆准分子对从实验和理论两方面被发现是效率最高的体系,更有希望被发展成为高能准分子宽带泵浦钠金属激光器。本工作还证明了采用大基组对结合能的高精度量化计算,对用于准分子宽带泵浦碱金属激光器的准分子对筛选是很好的评判标准。

Experimental and Theoretical Evaluation of the Absorption Coefficients of Excimer Pairs of Sodium with Noble Gases and Alkanes

The excimer-pumped sodium laser (XPNaL) is very important for its application in sodium guide star. However, the absorption coefficients (for the pumping source) of traditional excimer pairs, such as Na-He and Na-Ar, are very small. In this work, four systems (Na-Ar, Na-Xe, Na-CH₄, and Na-C₂H₆) are investigated based on both fluorescence experiment and theoretical binding energies obtained from highly accurate quantum chemistry calculations to determine better excimer pairs. The experiment results show that the peak area ratio of fluorescence intensity curves for the excimer pairs of Na-Ar, Na-Xe, Na-CH₄, and Na-C₂H₆ was 1.0 : 6.4 : 4.9 : 10.4. Meanwhile, using the CCSD(T) approach and basis set extrapolation, binding energies for these four systems were calculated as 52.8, 124.5, 117.7, and 150.0 cm^-1, respectively. Therefore, predication by quantum chemistry calculation was consistent with experimental results. The Na-C₂H₆ system was found to be the most efficient system both experimentally and theoretically, and has the potential to be used in the development of a high power XPNaL. This work also demonstrates that the binding energy from highly accurate quantum chemistry calculations with a large basis set is a very good criterion for the selection of excimer pairs for the excimer-pumped alkali laser (XPAL).