Valence and Rydberg excitations of 4-fluorotoluene in the 4.3–10.8 eV photoabsorption energy region

Abstract

This work reports on the first measurements of the lowest-lying singlet states as studied by photon spectroscopy for para-fluorotoluene, 4-C₇H₇F. Here we present the high-resolution vacuum ultraviolet photoabsorption spectrum in the 4.3–10.8 eV energy-range, with assignments supported by ab initio calculations (vertical excitation energies and oscillator strengths) at two different levels of theory, equation-of-motion coupled-cluster singles and doubles (EOM-CCSD) and time-dependent density functional theory (TD-DFT). The electronic state spectroscopy of 4-C₇H₇F reveals the main character of the transitions to be valence, mixed valence-Rydberg and Rydberg, with the associated vibronic series. The absolute cross-section measurements were obtained and used to estimate the photolysis lifetime of 4-fluorotoluene from the sea level up to limit of the stratopause (50 km) in the Earth's atmosphere.