The availability of accurate spectroscopic data on chloronium and its deuterated forms could greatly facilitate their identification in interstellar space. Despite their importance, very few spectroscopic data on this ion and even less on its deuterated forms HDCl + and D 2 Cl + are available in the literature. Experimentally, the first structural information on the chloronium ion was reported in 1986 by Kawaguchi and Hirota , who studied its ν 2 band with infrared diode laser spectroscopy. Saito et al. detected microwave spectral lines of H 2 35 Cl + in 1988. In the same year, Lee et al worked on the difference-frequency laser spectroscopy of the chloronium. These latter authors have observed the gas phase of the ν 1 and ν 2 fundamental bands of H 2 Cl + and determined its equilibrium structure. The rotational spectra of H 2 Cl + and HDCl + were measured by Araki et al using a submillimeter-wave spectrometer. Furthermore, theoretically, Botschwina computed a potential energy surface (PES) at coupled electron-pair approximation (CEPA) level and the vibrational frequencies for H 2 Cl + and its isotopologues HDCl + and D 2 Cl + . More recently, after the detection of the chloronium ion, Majumdar et al explored the possibility of finding the isotopologues of H 2 Cl + in and around the ISM. These authors used Moller-Plesset perturbation theory (MP2) along with a quadruple-zeta correlation consistent (aug-cc-pVQZ) basis set to optimize the geometry of chloronium and computed the harmonic vibrational frequencies of H 2 Cl + and its two deuterated isotopologues HDCl + and D 2 Cl + . Within their chemical modeling, they found that HDCl + could be efficiently formed in the gas phase and that the emission line should be strong enough to be observed.