With the good mass resolution (m/Δm) of about 650, the 35 Cl and 37 Cl isotopomers of p-chlorophenol have been separated successfully in our home made time of flight mass spectrometer (TOF-MS). One-color (1C), two-color (2C), resonant two-photon ionization (R2PI), and mass analyzed threshold ionization (MATI) spectra of the both isotopomers have been further recorded. Within the detection limit of our experiment, the band origins of the S 1 ←S 0 transition and the adiabatic ionization energies (IE) of 35 Cl and 37 Cl p-chlorophenol are measured to be the same. The band origins of the two isotopic species are determined to be 34813±2cm −1 by the 1C-R2PI experiment, and the adiabatic IE values are given to be 68094±15 and 68104±5cm −1 by the 2C-R2PI and MATI methods for the two isotopomers of 35 Cl and 37 Cl p-chlorophenol. Analysis on the S 1 ←S 0 transition energy of para substituted phenols suggests that the band origins are all red shifted from phenol regardless of the nature of the substituent, while the inductive effect plays an important role for the D 0 ←S 1 transition process. The spectral properties of the two isotopomers in the electronically excited S 1 and ionic ground D 0 states are similar, whereas the vibrational frequencies of some modes are slightly different by a few wavenumbers, displaying the isotope effect.