Ivanov VS, Sovkov VB, Li L, Lyyra AM, Lazarov G, Huennekens J
Institute of Physics, St. Petersburg State University, 1 Ulyanovskaya Street, St. Petersburg, Petrodvorets, 198904, Russia
J Mol Spectrosc. 1999 Apr;194(2):147-155. doi: 10.1006/jmsp.1998.7781.
An experimental study of the 3(3)Pig electronic state of 7Li2, using the Perturbation-Facilitated Optical-Optical Double Resonance (PFOODR) technique, was recently reported [A. Yiannopoulou et al., J. Chem. Phys. 103, 5898, (1995)]. However, due to the very small number of known 7Li2 A1Sigma+u approximately b3Piu window levels, only 13 ro-vibrational levels (spanning a range of vibrational levels designated upsilonx - 1 to upsilonx + 3 in that reference) could be observed. Dunham coefficients, based on the assignment upsilonx = 7, were found to fit the observed term values and give a qualitative fit to the intensities of the first six lines of the 3(3)Pig (upsilon = upsilonx, N = 11) --> b3Piu emission spectrum. However, due to the limited number of levels used in the fit, both the absolute vibrational numbering and the 3(3)Pig RKR potential curve obtained from the Dunham coefficients, must be considered to be uncertain. In the present work, we show that the previously reported 3(3)Pig RKR curve is unable to reproduce the experimental intensity distribution in the 7Li2 3(3)Pig (upsilonx = 7, N = 11) --> a3Sigma+u emission continuum. We report new experimental data for the 7Li2 3(3)Pig (upsilonx + 1, N = 11) --> a3Sigma+u bound-free continuum and discrete 3(3)Pig (upsilonx +/- 1, N = 11) --> b3Piu spectra obtained using the PFOODR experimental technique. We demonstrate that the correct vibrational numbering and an improved RKR potential curve can be obtained by analyzing the experimental term values in combination with all observed bound-free and discrete spectra. Finally, term values for four 6Li2 3(3)Pig ro-vibrational levels were obtained using PFOODR spectroscopy. The measured isotope shifts confirm the absolute vibrational numbering obtained from the present analysis. Copyright 1999 Academic Press.
最近有报道称，利用微扰辅助光学 - 光学双共振（PFOODR）技术对(^{7}Li_{2})的(3^{3}\Pi_{g})电子态进行了实验研究[A. 亚诺波洛乌等人，《化学物理杂志》103, 5898, (1995)]。然而，由于已知的(^{7}Li_{2})(A^{1}\Sigma^{+}{u})近似(b^{3}\Pi{u})窗口能级数量非常少，仅能观测到13个转动 - 振动能级（在该参考文献中跨越指定为(\upsilon_{x}-1)到(\upsilon_{x}+3)的一系列振动能级）。基于(\upsilon_{x}=7)的归属得到的邓纳姆系数，被发现能拟合观测到的项值，并对(3^{3}\Pi_{g}(\upsilon=\upsilon_{x},N = 11)\to b^{3}\Pi_{u})发射光谱的前六条谱线强度给出定性拟合。然而，由于拟合中使用的能级数量有限，从邓纳姆系数得到的绝对振动编号以及(3^{3}\Pi_{g})的RKR势曲线都必须被认为是不确定的。在本工作中，我们表明先前报道的(3^{3}\Pi_{g})RKR曲线无法重现(^{7}Li_{2})(3^{3}\Pi_{g}(\upsilon_{x}=7,N = 11)\to a^{3}\Sigma^{+}{u})发射连续谱中的实验强度分布。我们报告了使用PFOODR实验技术获得的(^{7}Li{2})(3^{3}\Pi_{g}(\upsilon_{x}+1,N = 11)\to a^{3}\Sigma^{+}{u})束缚 - 自由连续谱以及离散的(3^{3}\Pi{g}(\upsilon_{x}\pm1,N = 11)\to b^{3}\Pi_{u})光谱的新实验数据。我们证明，通过结合所有观测到的束缚 - 自由和离散光谱分析实验项值，可以得到正确的振动编号和改进的RKR势曲线。最后，使用PFOODR光谱学获得了四个(^{6}Li_{2})(3^{3}\Pi_{g})转动 - 振动能级的项值。测量得到的同位素位移证实了从本分析中得到的绝对振动编号。版权所有1999年，学术出版社。
