The (A) over tilde (2)A(')-(X) over tilde (2)A" electronic spectra of jet-cooled HPCl and DPCl have been obtained for the first time using the pulsed electric discharge technique with a precursor mixture of PCl3 and H-2 or D-2. From a combination of laser-induced fluorescence and wavelength resolved emission spectra, all of the vibrational frequencies in the ground and excited states of both isotopomers have been measured and vibrational force fields have been determined. Rotational analyses of the 0(0)(0) bands of both isotopomers showed small doublet splittings characteristic of an asymmetric top molecule with a single unpaired electron. From the rotational constants and the force fields, estimated equilibrium structures were derived with r(')(PH)=1.4158(23) Angstrom, r"(PCl)=2.0388(23) Angstrom, theta(')=95.02(27)degrees, and r"(PH)=1.4067(20) Angstrom, r(')(PCl)=2.0050(2) Angstrom, and theta(')=115.53(12)degrees. The experimental data firmly establish that the observed spectra and those previously obtained by chemiluminescence techniques [Bramwell , Chem. Phys. Lett. 331, 483 (2000)] are due to the HPCl free radical. (C) 2003 American Institute of Physics.