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Abstract

The harmonic and anharmonic force fields of the title compounds have been calculated at the ab initio self‐consistent‐field level using effective core potentials and polarized double‐zeta basis sets. Additional calculations for PH₂F employ larger basis sets and include electron correlation. Many rovibrational constants are predicted theoretically. The infrared spectra generated from the ab initio data have guided the experimental identification of PH₂F and PH₂Cl in the gas phase. High resolution Fourier transforminfrared spectra of these unstable molecules have been recorded for the first time. Rotational analyses for several bands are reported which provide accurate ground state constants and a precise characterization of a number of vibrationally excited states. The accuracy of the ab initio predictions for PH₂F and PH₂Cl is evaluated by comparisons with these experimental data.