Adiabatische Korrektur der Born-Oppenheimer-Näherung beim PbS/Adiabatic Correction of the Born-Oppenheimer Approximation of PbS

Abstract

Abstract The rotational microwave spectrum of PbS was measured in a frequency range from 65 to 105 GHz in order to determine the higher order isotopic effect of the rotational constant. From this we deduce (by calculating the nonadiabatic and the Dunham-correction) the adiabatic correction of the Born-Oppenheimer approximation, which depends linearly on the reciprocals of the masses of the two atoms in a diatomic molecule. Because of the small mass variation by isotopic substitution for the heavier molecules of the IV/VI-compounds the relative accuracy of the primary measurements must be of the order of 10 -6 . The least square fit of 112 rotational transitions yields a relative error of 10 -7 for the rotational constant Y 01 . The adiabatic corrections from Pb and S differ by a factor of 50, which was unexpected.