Transverse Relaxation of Optically Pumped Cesium Atoms

Transverse relaxation time of optically pumped cesium atoms in the ground state has been measured by use of the technique of multiple spin echo and cross-beam. Longitudinal relaxation time has also been measured by use of the pulse technique. The variation of relaxation time with the buffer gas pressure and the cell temperature has been studied in an unlined glass cell. Transverse relaxation time ( T 2 ) F + depends strongly on the cell temperature but longitudinal relaxation time T n does not. From the temperature dependence of ( T 2 ) F + , the spin-exchange cross section has been evaluated as 1.4×10 -14 cm 2 . Disorientation cross sections have been evaluated as follows: σ(( T 2 ) F + )=1.8×10 -23 cm 2 and σ( T n )=3.2×10 -24 cm 2 for cesium-neon collisions; σ(( T 2 ) F + )=5.9×10 -22 cm 2 and σ( T n )=2.5×10 -23 cm 2 for cesium-argon collisions. Diffusion coefficients for cesium in neon and in argon have been evaluated as 0.19 cm 2 /sec and 0.14 cm 2 /sec, respectively. For the interrelation of transverse and longitudinal relaxation times, it is revealed that (1/ T e +1/ T n ) is equal to (1/( T 2 ) F + +1/( T 2 ) F - ) in the case of extreme motion narrowing.