Raman spectra of solid P-4 have been recorded from 12 K up to room temperature using Fourier transform-Raman spectroscopy. The three Raman-active modes corresponding to T-d symmetry have been resolved, and line shifts depending on temperature and matrix environment have been measured. Two phase transitions have been observed at Tapproximate to80 K (irreversible) and Tapproximate to195 K (reversible) corresponding to the gamma-->beta and beta<---->alpha transitions, respectively. In the beta phase, the nu(2) mode is split into two lines, nu(split)approximate to7.7 cm(-1). The splitting of the nu(2) mode is an indication of a breaking of T-d symmetry for the beta phase. A matrix shift of approximate to3 cm-1 for P-4 in a N-2 matrix (1:5) was measured. Comparing experimental transitions of pure P-4 with literature values on matrix isolated P-4 in N-2 (1:1000) we can conclude that there is a matrix shift in nitrogen of between 6 and 9 cm-1 depending on vibrational mode. The line positions found for pure P-4 in the gamma phase at 12 K are nu(1)=599.8 cm(-1), nu(2)=361.6 cm(-1), and nu(3)=459.0 cm(-1). The corresponding values in the alpha phase at 220 K are nu(1)=598.8 cm(-1), nu(2)=360.6 cm(-1), and nu(3)=458.0 cm(-1). The present work also adds valuable insight into the behavior of other potential molecules with similar T-d structure such as N-4(T-d). (C) 2003 American Institute of Physics.