Spin polarization of 87Rb atoms with Xe gas and high-pressure buffer gas in a cubic cell

Hoon Yu,Jai Seung Yoo

doi:10.1063/1.5080704

Abstract

We simulated the optical pumping rate of 87Rb atoms with Xe and high-pressure buffer gas in a cubic cell. We calculated absorption cross-section as a function of pumping laser frequency by considering a pressure and Doppler broadening as gas temperature varies from 364 K to 414 K. In a steady state the spin polarization and the atomic population of 87Rb atoms were obtained by optical pumping in each ground state. We calculated the optimum beam waist, linewidth and detuning of pumping beam to achieve higher population of polarized atoms at cell parameters such as temperature, size. We simulated that the optimum beam waist is 0.3 times of cubic cell length at 250 Torr of di-nitrogen and 50 Torr of Xe gas pressure. The optimum laser beam linewidth parabolically increases with increasing the temperature in range of few ten kelvin and it exponentially decrease with increasing the cubic cell length. We also observed that few ten GHz detuned laser frequency increases the optical pumping rate. These numerical results show appropriate experimental parameter as a function of cell temperature and size to get maximum population of spin polarized atoms in given temperature range.

Highlights

We simulated that the optimum beam waist is 0.3 times of cubic cell length at 250 Torr of di-nitrogen and 50 Torr of Xe gas pressure
Xe polarization occurred by spin exchange collision between optically pumped alkali and noble gases was measured as the function of cell temperature
Average spin polarization probability of 87Rb atoms is calculated from eq (6) as shown in Fig. 3 in a cubic cell as a function of the pumping laser line width and beam waist

Summary

INTRODUCTION

We can selectively populate the atomic spin state from thermal equilibrium population by using circularly polarized optical pumping laser beam. Spin polarized alkali-atom achieved by optical pumping in vapor form have been applied in the fields of atomic clocks, atomic magnetometer, magnetic resonance imaging and nuclear magnetic resonance gyroscope. Since the spin state of noble atomic gases has a long spin relaxation time, alkali atom spin is used to manipulate the spin state of noble atoms through spin exchange collisions. In experiment high temperature gas around 380K and few hundred Torr high-pressure buffer gases are preferred for a high spin exchange collision rate. Absolute absorption in Rb vapor gas medium was theoretically and experimentally studied for D line transition. The spin polarization efficiency of optically pumped Rb atoms was studied as a function of gas pressure and laser power. Xe polarization occurred by spin exchange collision between optically pumped alkali and noble gases was measured as the function of cell temperature.. In experiment high temperature gas around 380K and few hundred Torr high-pressure buffer gases are preferred for a high spin exchange collision rate.. The spin polarization efficiency of optically pumped Rb atoms was studied as a function of gas pressure and laser power.. Xe polarization occurred by spin exchange collision between optically pumped alkali and noble gases was measured as the function of cell temperature.. We consider light attenuation through the gas mixture to calculate spin polarization in a cubic cell. As a result of light absorption and populate atoms in each energy level for the steady state, the spin polarization of rubidium gas in a cubic cell was obtained as a function of a laser line width, beam size, cell temperature and cell size

THEORY FOR CALCULATING OPTICAL PUMPING

NUMERICAL RESULTS

CONCLUSION