(2 + I) REMPI spectra of HX (X=Cl, Br and I) have been recorded and analyzed by simulation calculations to derive rotational constants, band origins and isotope shift values for a number of vibrational bands of Omega = 0 states. Our data for HCl compare nicely with those derived by Green et nl. by conventional analysis methods [D. S. Green et al., J. Mel. Spectrosc. 150, 303, 354, 388 (1991); D. S. Green and S. C. Wallace, J. Chem. Phys. 96, 5857 (1992)]. New spectroscopic parameters were derived for eight vibrational bands which are assigned to the V((1)Sigma(+)) state, for upsilon＇=4 of the E((1)Sigma(+)) state, as well as for five new bands in HBr. New spectroscopic parameters were derived for four vibrational bands which are assigned to the V state and for upsilon＇=1 of the E state in HI. Anomalies observed in energy level spacings, rotational parameters and isotope shift values are interpreted as being largely due to homogeneous interactions between the V and the E states. It is argued that the interaction causes a compression of rovibrational levels in the E state manifold but an expansion of levels in the V stale manifold, something which might be expected for a Rydberg to ion-pair interaction. Variations observed in the intensity ratio of O and S line series to Q line series in vibrational bands of the E and V slates for HCl and HBr are discussed and mechanisms of two-photon excitation processes are proposed.