With a high-resolution two-crystal vacuum spectrometer, the phosphorus
K beta emission spectra in fluorescence are measured for H3PO3 (=H2PH
O3), H3PO4, Li3PO4, Na3PO4 . 12H(2)O, Na2HPO4, NaH2PO4, K3PO4 . nH(2)O
, K2HPO4, KH2PO4, Ca-3(PO4)(2), CaHPO4 . 2H(2)O, Ca(H2PO4)(2) . H2O, C
aHPO3 . H2O, Ca(H2PO2)(2) and NH4H2PO4. In the phosphate compounds, a
weak peak is observed on the high-energy side of the main peak K beta(
1) and related to a molecular orbital of t(2) symmetry in the PO43- io
n. It is shown that the phosphorus K beta emission spectra are influen
ced by ligand substitution and cations. The measured KP emission spect
ra of Li3PO4, Na3PO4 . 12H(2)O, K3PO4 . nH(2)O and Ca-3(PO4)(2) are pr
esented along with the previously reported P-K absorption spectra of t
hese phosphate compounds. The emission and absorption spectra are inte
rpreted in terms of available molecular orbitals of the PO43- ion.