Infrared study of solid phosphine

Infrared spectra of two crystalline forms of PH3 and PD3 are reported. The modification studied at 35°K displays broad structureless absorption bands but the form below the transition temperature at about 30°K has a complexity of sharp spectral lines. From results of the temperature effect on the spectra and from studies of isotopic impurities in PH3 and PD3 host crystals, the authors speculate that this lower temperature form of phosphine may have a structure with a primitive cell containing as many as 12 molecules occupying six different sets of sites.