Measurement of the Electric Dipole Polarizabilities of the Homonuclear Alkali Dimer Molecules and Heteronuclear Alkali Dimer Binary Compounds.

The average static electric dipole polarizabilities of homonuclear and heteronuclear alkali dimers were measured by spatial deflection of a molecular beam in an inhomogeneous electric field. The congruent electric and magnetic inhomogeneous fields enables removal of the monomer portion of the beam via the Stern-Gerlach force while the remaining dimer portion is deflected via the electric polarization force. It is assumed that the atomic and molecular constituents possess modified Maxwell-Boltzmann velocity distributions. The Mach number is introduced to describe the sonic properties of the molecular beam. The dimer data analysis consists of a two parameter least squares best fit of the experimental deflection curves to computed ones. The two independent parameters are the dimer polarizability and the Mach number. Beams of NaK and KCs alkali molecules were observed and investigated. Here the deflected curves reflect both the permanent dipole moment and the induced (polarizability) dipole moment. Our experimental observations and numerical analyses show that the presence of the permanent dipole moment shifts the deflection curve of the heteronuclear molecule so its effective polarizability approaches that of the low mass homonuclear dimer. Assuming that the permanent dipole moments are known from theoretical calculations the average static dipole polarizabilities for NaK and KCs were obtained. The measured static dipole polarizabilities in (A^3 ) are: Li_2(948^{circ }K) = 35 +/- 2; Na _2(676^{circ}K) = 39 +/- 3; NaK(612^ {circ}K) = 51 +/- 3; K_2(542^{circ}K) = 77 +/- 5; Rb_2(527 ^{circ}K) = 79 +/- 5; KCs(488^{circ}K) = 89 +/- 5; Cs_2(480 ^{circ}K) = 104 +/- 6.