Spectra of H+, 35Cl+, H35Cl+ and their isotopologues, due to resonance enhanced multiphoton ionization (REMPI) of HCl via the F1Δ2 (v’=1) Rydberg and V1∑+ (v’=13, 14) ion-pair states are recorded in a range of 84800-85700 cm-1. Perturbation effects indicate the resonance interaction between the F1Δ2 (v’=1) and V1∑+ (v’=14) states. An improved model for analyzing relative signal intensity of spectrum, based on state interaction and photofragmentation process, is used to analyze the F1Δ2 (v’=1) spectral data. Interaction strength (W’=0.6 cm-1) and a predissociation parameter (γ=0.025) are derived. Comparable interaction strength and unperturbed spectroscopic parameters are derived from the deperturbation analysis of line positions for the F1Δ2 (v’=1) and V1∑+ (v’=13, 14) spectra. The study indicates that the formation of the H+ and Cl+ ions via two-photon resonance excitation of F1Δ2 (v’=1) state is associated with the state interaction. An indication of the line-shift of F1Δ2 (v’=1) state spectrum due to Rydberg-to-Rydberg state interaction is also found. The nonzero γ value suggests that the predissociation of the F1Δ2 state is important.