ECAMP 15

We present the determination of the intermolecular dissociation energies of M-Ar1-3 (Where M= Naphthalene, Naphthol and 2,2 PBI) complexes by measuring the sequential desorption energies of Ar atoms from the aromatic surface. The dispersion-dominated M-Ar1-3 complexes were produced in the gas phase and characterized using resonant two-photon ionization (R2PI) spectroscopy. The disappearance of Franck-Condon active vibrational bands in the R2PI spectrum was utilized to determine the D0(S1) values of dispersively bound molecular complexes. The energy required to desorb a single Ar atom from the Np-Ar, Np-Ar2, and N-Ar3 complexes were bracketed as 522 ± 20, 522 ± 20, and 489 ± 53 cm-1, respectively. The corresponding dissociation energies D0(S1) were determined to be 522 ± 20, 1044 ± 40, and 1533 ± 93 cm -1, respectively for n=1, 2 and 3. The ground state dissociation energy D0(S0) was calculated by subtracting the Δν shift of the origin band in the excited state D0(S1), and the values were obtained as 507 ± 20, 1013 ± 40, and 1489 ± 93 cm−1, respectively, for Np-Ar, Np-Ar2, and Np-Ar3 complexes. The calculated dissociation energies obtained using D4 corrected B3LYP, PBE0 and BH-LYP levels using def2-TZVPP basis set, have shown good agreement with the experimental data, with the best agreement at PBE0 method. The current investigation highlights an effective laser spectroscopic approach to precisely measure the desorption and dissociation energies of non-covalently bound complexes of polycyclic aromatic hydrocarbon molecules.