Benzene–argon triplet intermolecular potential energy surface

The benzene–Ar lowest energy triplet state $T1$ intermolecular potential energy surface is evaluated using coupled cluster methods and the aug-cc-pVDZ basis set extended with a set of $3s3p2d1f1g$ midbond functions. This surface is characterized by an absolute minimum of −392.5 cm⁻¹, where the argon atom is located on the benzene $C6$ axis at a distance of 3.5153 Å, and has a general shape very close to the ground state $S0$ and the first singlet $S1$ excited state surfaces. Using the $T1$ potential, the intermolecular vibrational energy levels were evaluated and the results compared to those for the ground $S0$ and the excited $S1$ states. The calculated fundamental frequencies for the bending and the stretching modes are lower than those in the $S1$ state. The calculated data for the $T1$ state is expected to have the same accuracy as previously calculated data for the $S1$ state.