Evaluation of Expansion Coefficients from Optimal Fitting Parameters for the Analysis of Spectra of Diatomic Molecules and an Application to LiH

The inversion of diatomic Born–Oppenheimer-breakdown corrections

“…Uehara and Ogilvie [15] have considered in detail the BOB corrections to the Y kl for kl ¼ 01; 02; 03; 04; 10; 11; 12; and 20, and have verified that these corrections can be written in terms of the expansion coefficients ofR R i andS S i , and are independent of the arbitrary lower limit of integration, equivalent to the term A i 0 . Consideration of the indeterminacy due to A i 0 gives a good illustration of the truncation problem.…”

“…Alternatively, the U kl can all be calculated from U 10 ¼ U x , U 01 ¼ U B , and the Dunham potential constants a n , as employed in the methods of Maki et al [21] and Uehara [31,33]. The redundancies in the D kl [15] involve terms with l P 4, and these are seldom required in practice. 2.…”

“…This approach makes it unnecessary to consider the redundancies among the U kl [13] and D kl [15] parameters of Eq. (54), but it can be less obvious which combinations of BO and BOB parameters are determinable from the vibration-rotation energy levels.…”

“…2. Constraining the t i n coefficients to values calculated ab initio [15,29,35] or from Stark and Zeeman data, using Eq. (35) [28,30,32].…”

“…The BOB corrections have been widely studied for the LiH molecule [15,[18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35] because it has two light atoms with large fractional isotopic changes in mass, the two isotopes of the Li atom can be studied at natural abundance, and there is a large amount of pure rotational data because of the existence of a dipole moment.…”