Dipole and quadrupole (hyper)polarizability for the asymmetric stretching of carbon dioxide: Improved agreement between theory and experiment

We report a theoretical investigation of electric multipole moments and the dipole and quadrupole (hyper)polarizability for the asymmetric stretching of carbon dioxide. The dependence of the properties on the displacement parameter ΔR is not uniform. At the CCSD(T) level of theory the dipole moment varies around the equilibrium position as μ ( Δ R ) / ea 0 = - 1.21 Δ R + 0.02 Δ R 3 . At the MP2 level we find for the dipole–quadrupole polarizability A z , zz ( Δ R ) / e 2 a 0 3 E h - 1 = 23.6 Δ R - 1.2 Δ R 3 , A x , zx ( Δ R ) / e 2 a 0 3 E h - 1 = 17.7 Δ R + 0.9 Δ R 3 . Our best value for the derivative d μ d Δ R e = - 1.21 e is in very good agreement with experiment. For the mean polarizability we obtain d 2 α ¯ d Δ R 2 e = 0.68 e 2 a 0 E h - 1 which lifts the existing ambiguity for the respective experimental findings.