The NMR spin–spin coupling constant 1J(31P,1H) in an isolated PH3 molecule

Abstract

We present new experimental and calculated values of the indirect spin–spin coupling constant ¹J(³¹P,¹H) in the PH₃ molecule. The line shape analysis of ¹H and ³¹P gas-phase NMR spectra recorded at several densities of PH₃, followed by extrapolation of the results to the zero-density limit, gives 176.18(2) Hz as the experimental value at 300 K. The coupled-cluster singles-and-doubles (CCSD) model used in the quantum chemical ab initio calculation gives 187.86 Hz as the nonrelativistic equilibrium geometry value; adding the relativistic and temperature corrections we obtain ¹J(³¹P,¹H) = 177.14 Hz at 300 K. The comparison of this ab initio result with the experimental value shows that proper analysis of nuclear relaxation in the gas phase is essential and leads to very good agreement between theory and experiment.