Combined experimental and theoretical treatment of the dipole polarizability of P4 clusters -: art. no. 053202

The frequency dependence of the dipole polarizability alpha(omega) of P-4 is obtained from refractive index measurements on gaseous phosphorus by means of asymmetric white-light interferometry. The experimental results obtained in the range between 10 000 and 30 300 cm(-1) yield an extrapolated static value of alpha = 91.71(92)e(2)a(0)(2)E(H)(-1). An extensive theoretical study, based on finite-field many-body perturbation theory and coupled cluster methods, leads to a theoretical estimate at zero frequency of alpha approximate to 93.2(0.9) e(2)a(0)(2)E(H)(-1) at the experimental bond length R-0 = 2.1958 Angstrom. For the symmetric stretch of the molecule the dipole polarizability of P-4 varies around R-0 as [alpha(R)-alpha(R-0)]/e(2)a(0)(2)E(H)(-1)=34.02 Delta R+3.68 Delta R-2-0.29 Delta R-3 showing an essentially linear dependence on the change of the P-P bond distance Delta R = (R-R-0)/a(0) The dipole polarizability per atom is significantly smaller than that of the phosphorous atom 25.22 e(2)a(0)(2)E(H)(-1). This differs from the corresponding change of alpha in the homologous As-4 cluster, where the single atom value is very close to the polarizability per atom of the cluster.