Kinetics of the Excited Singlet and Triplet States of Vapor-Phase Phenanthrene

Abstract

The lifetime, τ=1/k, of the first excited singlet state of vapor‐phase phenathrene has been measured as a function of pressure and excitation wavelength. Excitation in the first singlet absorption band (3400–3100 Å) resulted in τ=50±2 nsec and excitation in the second singlet band resulted in τ=45±2 nsec. The singlet‐to‐triplet intersystem‐crossing efficiency, Φ_ST=k_ST/k, was measured and found to be Φ_ST=0.88±0.05. From the measured absorption and emission spectra, the fluorescence efficiency, Φ_F=k_F/k, was calculated to be Φ_F=0.07. Internal conversion from the lowest excited singlet state to the ground state was shown to be very inefficient (Φ_IC2 sec⁻¹.