Dunham coefficients for the X 1 Σ + ground state of BH and BD

Ab Initio spectroscopic characterization of borane, BH, in its electronic state

“…Note that these are the mass‐dependent values, incorporating both the adiabatic and nonadiabatic effects. The predicted equilibrium internuclear distances are in perfect agreement with the corresponding experimental values of 1.23218 and 1.23087 Å, thus lending plausibility to the level of theory applied in this work.…”

“…To further assess the predictive power of the potential energy functions of BH determined in this work, the effective equilibrium internuclear distances for the 11 BH and 11 BD isotopologues were derived using the best calculated vibration‐rotation energy levels and compared with the recent experimental data. As is customary in the experimental spectroscopic studies, the calculated vibration‐rotation energies of both the 11 BH and 11 BD molecules (with and ) were fit to the Dunham energy level expression . The effective equilibrium distances were then derived from the coefficient ( , the equilibrium rotational constant) using the atomic masses of boron and hydrogen.…”

“…To account for the adiabatic effects, the diagonal Born-Oppenheimer correction (DBOC) [54,55] was calculated for four isotopologues: 11 BH, 11 BD, 10 BH, and 10 BD. The DBOC was determined using the spin-restricted open-shell Hartree-Fock (ROHF) method and the restricted-active-space configuration interaction (RAS CI) [56] method, both in conjunction with the aug-cc-pCVTZ basis set.…”

“…In the vicinity of the equilibrium configuration of the main isotopologue 11 BH, the DBOC was determined to be 360 cm 21 (1.639 mE h) with the ROHF method and 371 cm 21 (1.689 mE h) with the RAS CI method. Using the latter method, the DBOC was determined for the 11 BD, 10 BH, and 10 BD isotopologues to be 318, 397, and 345 cm 21 , respectively. The DBOC values were calculated at the same set of points as the Born-Oppenheimer potential energy functions discussed above and were subsequently added to the CV1F1R1S total energies.…”

“…Borane, BH, is the simplest among boron hydrides, the compounds forming various cage-type structures. [1] The BH molecule was the subject of several spectroscopic studies in the gas phase, [2][3][4][5][6][7][8][9][10] and its high-resolution electronic-vibrationrotation spectra were investigated from the microwave to ultraviolet region. Despite a large body of experimental data, accurate spectroscopic constants for the BH isotopologues including less-abundant isotopes, 10 B and D, are somewhat scarce.…”