The LIF excitation spectra of jet-cooled 3-aminobiphenyl

The S₁←S₀ transitions in 3-aminobiphenyl were studied in a supersonic jet by laser-induced fluorescence. The results were compared with ab initio HF, CIS and DFT/SCI calculations and with experimental data for the biphenyl, 1-phenylpyrrole and 2-phenylindole. The equilibrium geometry of the 3-aminobiphenyl in the S₁ state is non-planar with the dihedral angle between two phenyl rings about 5.4° (CIS/6-31G^*). The torsional potential in the S₁ state has been determined by fitting the one-dimensional potential of the form V(φ)= 2 ∑_n V_n(1−cos nφ), to reproduce the observed level spacing (V₂=3420, V₄=−378, V₆=−32.8 and V₈=−2.9 cm⁻¹). The observed deuteration effects seem to confirm this potential.