CrH and CrH2 molecules: ESR and optical spectroscopy at 4 °K

CrH and CrD molecules have been trapped in solid argon at 4 °K. Infrared spectra, when the large anharmonicity is accounted for, yield predicted gas phase vibrational parameters in the ground state ωe =1615 cm−1 and ωexe=17 cm−1. ESR spectra clearly establish that the molecule has a 6Σ ground state with zero-field-splitting ‖D‖=0.34(1) cm−1 in solid argon and approximate hyperfine coupling constants ‖A (H) ‖=49(5) MHz, ‖A⊥(53Cr) ‖=53(5) MHz, and g⊥?g∥=ge. Several ’’extra lines’’ (off-principal-axis absorptions) in the ESR support the assignment. CrH2 (and CrD2, CrHD) was observed in the IR spectra and may also have been detected in the ESR, which tentatively suggest a S=2 molecule with ‖D‖?0.02 cm−1.