Leading order nonadiabatic corrections to rovibrational levels of H2, D2, and T2

Authors:

• Krzysztof Pachucki,
• Jacek Komasa

Abstract

An efficient computational approach to nonadiabatic effects in the hydrogen molecule (H2, D2, and T2) is presented. The electronic wave function is expanded in the James-Coolidge basis set, which enables obtaining a very high accuracy of nonadiabatic potentials. A single point convergence of the potentials with growing size of the basis set reveals a relative accuracy ranging from 10−8 to 10−13. An estimated accuracy of the leading nonadiabatic correction to the rovibrational energy levels is of the order of 10−7 cm−1. After a significant increase in the accuracy of the Born-Oppenheimer and adiabatic calculations, the nonadiabatic results presented in this report constitute another step towards highly accurate theoretical description of the hydrogen molecule.