Scalar Dipole Polarizabilities Research Articles

Proton scalar dipole polarizabilities from real Compton scattering data using fixed-t subtracted dispersion relations and the bootstrap method

We perform a fit of the real Compton scattering (RCS) data below pion-production threshold to extract the electric (αE1) and magnetic (βM1) static scalar dipole polarizabilities of the proton, using fixed-t subtracted dispersion relations and a bootstrap-based fitting technique. The bootstrap method provides a convenient tool for including the effects of the systematic errors on the best values of and , and for propagating the statistical errors of the model parameters fixed by other measurements. We also implement various statistical tests to investigate the consistency of the available RCS data sets below pion-production threshold, and conclude that there are not strong motivations to exclude any data point from the global set. Our analysis yields and , with p-value = 12%.

Determination of the scalar polarizabilities of the proton using beam asymmetry $\Sigma_{3}$ Σ 3 in Compton scattering

The scalar dipole polarizabilities, $\alpha_{E1}$ and $\beta_{M1}$, are fundamental properties related to the internal dynamics of the nucleon. The currently accepted values of the proton polarizabilities were determined by fitting to unpolarized proton Compton scattering cross section data. The measurement of the beam asymmetry $\Sigma_{3}$ in a certain kinematical range provides an alternative approach to the extraction of the scalar polarizabilities. At the Mainz Microtron (MAMI) the beam asymmetry was measured for Compton scattering below pion photoproduction threshold for the first time. The results are compared with model calculations and the influence of the experimental data on the extraction of the scalar polarizabilities is determined.

Dipole and quadrupole polarizabilities of Ni II and parameters of an effective potential for Ni I Rydberg states

The relativistic configuration interaction method has been used to evaluate the bound and continuum portions of summation expressions for the dipole and quadrupole polarizabilities, yielding the Ni II results αD,0 = 7.686 au for 3d9 2D3/2 and αQ,0 = 61.940 au for 3d9 2D5/2. The experimental value for the latter is estimated to be 55(8) au. From the reduced matrix elements, we have evaluated the first non-adiabatic scalar dipole polarizability βD,0 for 2D5/2 to be 9.243 au (experimental estimate is 8.9 (1.2)) and the off-diagonal tensor dipole polarizability αD,2 to be = −0.220 au (experimental estimate is −0.04 au). Significant cancellations occur in this last quantity (see text).

Optical spectroscopy of high-LRydberg states of argon

High-$L$ fine structure patterns in $n=9$ and $n=17$ Rydberg levels of argon have been studied using a Doppler-tuned $\mathrm{C}{\mathrm{O}}_{2}$ laser and a fast beam of argon atoms. Analysis of the measured pattern using the polarization model yields the scalar dipole polarizability and quadrupole moment of the $^{2}P_{3∕2}$ ${\mathrm{Ar}}^{+}$ ion. The results are ${\ensuremath{\alpha}}_{S}=6.83(8){a}_{0}^{3}$ and $Q=\ensuremath{-}0.5177(15)e{a}_{0}^{2}$. Within the precision of this study, no vector component of the structure was observed.

Method of the reduced-added Green function in the calculation of atomic polarizabilities

The Green function in the quantum defect theory provides an exact account for high-excited and continuum electronic states. We modify it by taking into account the ground and low-excited states using their wave functions calculated ab initio. As an application, we present a simple and efficient semianalytical method for the calculation of atomic electric frequency-dependent scalar dipole polarizability, for both real and imaginary frequencies. The polarizabilities calculated for some atoms (Li, Na, K, Be, Mg, Ca, Si, P, S, O, Al, Ge, C, N, F, He, Ne, Ar, Kr, and Xe) are compared with existing methods of computational quantum chemistry and with experiments; good accuracy of the proposed method is demonstrated.

High precision measurement of the static dipole polarizability of cesium.

The cesium 6(2)S(1/2) scalar dipole polarizability alpha(0) has been determined from the time-of-flight of laser cooled and launched cesium atoms traveling through an electric field. We find alpha(0)=6.611+/-0.009 x 10(-39) C m(2)/V=59.42+/-0.08 x 10(-24) cm(3)=401.0+/-0.6a(3)(0). The 0.14% uncertainty is a factor of 14 improvement over the previous measurement. Values for the 6(2)P(1/2) and 6(2)P(3/2) lifetimes and the 6(2)S(1/2) cesium-cesium dispersion coefficient C6 are determined from alpha(0) using the procedure of Derevianko and Porsev [Phys. Rev. A 65, 053403 (2002)]].

Relativistic corrections to the dipole polarizability of the ground state of the molecular ionH2+

The recently reported precise experimental determination of the dipole polarizability of the H_2^+ molecular ion ground state [P.L. Jacobson, R.A. Komara, W.G. Sturrus, and S.R. Lundeen, Phys. Rev. A 62, 012509 (2000)] reveals a discrepancy between theory and experiment of about 0.0007a_0^3, which has been attributed to relativistic and QED effects. In present work we analyze an influence of the relativistic effects on the scalar dipole polarizability of an isolated H_2^+ molecular ion. Our conclusion is that it accounts for only 1/5 of the measured discrepancy.