Abstract
The harmonic force constants, infrared and ultraviolet spectra of NH3, are studied theoretically. The calculation is based on a single‐center configuration interaction wavefunction; the corresponding energy is differentiated analytically. The calculated force constants are discussed, particularly the interaction force constants. The theoretical infrared spectra of NH3 and ND3 agree reasonably well with the observed spectra. The ultraviolet spectrum of NH3 is also studied; the lowest singlet—singlet transitions are found to be 1A11A1 and 1E1A1 (in C3v notation).