Electric Polarizability and Hyperpolarizability of Carbon Monoxide

We report an extensive ab initio study of the electric dipole polarizability and hyperpolarizability of carbon monoxide. The bond length dependence of the molecular properties has been determined from finite-field complete fourth-order many-body perturbation theory and coupled cluster calculations with very large, well-optimized basis sets of Gaussian functions. The mean dipole polarizability ᾱ and the anisotropy Δα vary around the experimental bond length of R e = 2.132 221 a 0 as ᾱ( R )/ e 2 a 0 2 E h -1 = 13.19 + 5.52( R − R e ) + 1.74( R − R e ) 2 − 0.35( R − R e ) 3 − 0.33( R − R e ) 4 and Δα( R )/ e 2 a 0 2 E h -1 = 3.66 + 8.28( R − R e ) + 3.32( R − R e ) 2 − 0.24( R − R e ) 3 − 0.42( R − R e ) 4 . The mean first dipole hyperpolarizability β varies as β( R )/ e 3 a 0 3 E h -2 = 28.0 − 7.0( R − R e ) − 5.6( R − R e ) 2 − 8.7( R − R e ) 3 + 2.1( R − R e ) 4 and the mean second dipole hyperpolarizability γ̄ as 10 -2 γ̄( R )/ e 4 a 0 4 E h -3 = 15.3 + 3.4( R − R e ) + 13.3( R − R e ) 2 + 1.8( R − R e ) 3 − 2.6( R − R e ) 4 . Our best values for the respective static limits at the ground vibrational state are ᾱ = 13.15 e 2 a 0 2 E h -1, Δα = 3.68 e 2 a 0 2 E h -1, β = 26.5 e 3 a 0 3 E h -2, and γ̄ = 14.8 × 10 2 e 4 a 0 4 E h -3 . Relying on previous estimates of the dispersion of the hyperpolarizability (Sekino, H.; Bartlett, R. J. J. Chem. Phys . 1993, 98, 3022), we estimate for the hyperpolarizability the values of β = 30.1 ± 0.6 e 3 a 0 3 E h -2 and γ̄ = (17.9 ± 0.9) × 10 2 e 4 a 0 4 E h -3 at 694.3 nm, in excellent agreement with the available experimental results of 30.2 ± 3.2 e 3 a 0 3 E h -2 and 1730 ± 50 e 4 a 0 4 E h -3, respectively.