Emission spectra obtained from bulk-gas methinophosphide (HCP) have been interpreted by means of a Lie algebraic theory that describes explicit non-rigidity of the molecular framework. Fluorescence accompanying selective excitation of Ã1 A?-X?1 ?+ vibronic bands was dispersed under moderate resolution, with substantial activity of the v2 H-C-P bending mode reflecting the bent-from-linear nature of the à ? X? transition. Aside from furnishing an economical parameterization for energy level patterns, the algebraic treatment permits Franck-Condon intensities to be evaluated quantitatively. The equilibrium structure deduced for the Ã1A? state is in good accord with quantum chemistry calculations except for substantially less than predicted elongation of the C-P bond upon electron promotion. © 2002 Elsevier Science B.V. All rights reserved.