Mass Spectrometric Determination of the Dissociation Energies of CuTb(g), CuDy(g), and CuHo(g)

The enthalpy changes of the reactions magnified image (M = Tb, Dy or Ho) could be determined by Knudsen effusion mass spectrometric studies vaporizing pure Cu and M‐Cu alloys. The following dissociation energies at 0 K were obtained for Cu2(g), TbCu(g), DyCu(g) and HoCu(g) in kJ mol−1: 190.2 ± 5.4, 187 ± 19, 140 ± 19 and 139 ± 19. The appearance potentials of the single charged ions of these molecules could be determined as 7.8 ± 0.4, 5.3 ± 0.3, 5.4 ± 0.4 and 5.3 ± 0.3 eV, respectively. The experimental dissociation energies for the heteronuclear diatomic molecules are compared with the theoretical predictions of the Pauling model of the polar bond.