InP, InAs, and InSb diatomics have been prepared by laser vaporization of the corresponding crystals into neon, argon, and/or krypton gases and condensed on a gold surface at 4 K. Their infrared spectra (10-4800 cm(-1)) were observed in absorption. The zero-field splittings [(3) Sigma(-)( 1X(2))-(3) Sigma(-)(O(+)X(1))] in the ground states of InAs and InSb were observed and verified by the broadening effects of applied magnetic fields of up to 4 T. For InAs, a Franck-Condon envelope with (0,0) at 3600 cm(-1) was also observed and assigned to the vibrational progression of a low-lying A(3)II excited state. A strong absorption in these spectra was attributed to the nu(3) stretching mode of the triatomic In(2)X (X = P, As, Sb) molecules. Trends in the spectra are quite similar to those observed earlier in the GaX series.