The ground state infrared spectra of several isotopic forms of the CdH and ZnH radicals

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Abstract
The infrared spectra of six isotopic forms of cadmium monohydride, [116CdH (7.6%), 114CdH (28.9%), 113CdH (12.3%), 112CdH (24.1%), 111CdH (12.7%), and 110CdH (12.4%)] and four isotopic forms of zinc hydride [68ZnH (18.6%), 67ZnH (4.1%), 66ZnH (27.8%), and 64ZnH (48.9%)] have been observed in natural abundance in their ground electronic state (2∑+) in the gas phase using a diode laser spectrometer. A number of transitions of 108CdH (0.9%) and 106CdH (1.2%) and 70ZnH (0.6%) were also observed, but too little data was accumulated to allow a good analysis. The hydrides were produced by reaction of hydrogen with metal vapor at elevated temperature in an electric discharge. The analysis of the experimental data was carried out in two ways. (a) A complete set of Dunham parameters and spin–rotation parameters (γ parameters) was determined for each isotopic species of the two radicals and (b) a set of mass‐independent parameters were calculated for both ZnH and CdH. Since only information over the isotopic species of the heavy atom was produced in each case, effects arising from a breakdown of the Born–Oppenheimer approximation were negligible. The effects of the strong anharmonicity present in these two molecules on the values of the parameters are discussed.