A pseudostate method for computing photon-atom scattering cross-sections

Abstract

A computational method is developed for photon-atom scattering cross-sections given by the p • A interaction, which dominates scattering at low frequencies. Our method is simple and intuitive, and has the advantage of being extremely adaptable-it can be extended to higher-order scattering processes and applied to any atom. The scattering cross-sections calculated in this thesis provide a more complete picture of the photon-atom interaction than is currently available, which is useful for high-precision atomic, molecular and optical (AMO) experiments and has applications in astrophysics and spectroscopy.

Rayleigh and Raman Scattering from Alkali Atoms

“…For Rayleigh scattering on the ground state, we compared our results with the low energy approximation used in the Los Alamos National Lab ATOMIC opacity and plasma modelling code [5] and found good agreement at low energies for all alkali atoms. We have also found good agreement with the lithium and sodium ground state Rayleigh scattering cross sections of Grunefeld [15]. As discussed earlier, the convergence of the ground state Rayleigh scattering cross section is particular fast and the good agreement is expected.…”

“…We investigated the effect of the different forms of the dipole operator, the length, velocity, and modified length forms Equation (15). This is illustrated in Figure 2 for cesium.…”

“…Rayleigh and Raman scattering cross sections for the ground state of cesium calculated using the complex scaling (CS) method. We compare cross sections for different forms of the dipole operator, these being the length (L) gauge, velocity (V) gauge, and modified length (M) defined by Equation (15). The difference between the length and velocity gauge cross sections is due to the use of an l-dependent potential.…”

“…Calculations of Rayleigh and Raman cross sections for scattering on alkali atoms are scarce and there are no experimental results. Apart from the results that are presented in the thesis of Grunefeld [15], we could only locate calculations due to Sadeghpour and Dalgarno [12] for cesium. In Figure 10, we compare with the results of Sadeghpour and Dalgarno [12] and find good agreement for the cesium 6s → 6s Rayleigh cross section, but not for the 6s → 7s Raman cross section.…”

“…Drühl [14] considered anti-Stokes Raman scattering on atomic iodine for small incident photon energies, where the infinite summation over intermediate states was approximated while using sum rules. Grunefeld [15] used complex polarizabilties and hyperpolarizabilties to calculate Rayleigh and Raman scattering on various targets, including lithium and sodium.…”