Low-field orientation dependence of 3He relaxation in spin-exchange cells

We have observed a significant dependence of 3He longitudinal relaxation times in glass spin-exchange optical pumping (SEOP) cells due only to the physical orientation of the cell in a 3 mT (30 G) applied magnetic field. The cells had no previous exposure to higher fields or were thoroughly degaussed prior to being measured. The presence of rubidium metal and heating of the cells associated with the SEOP process is necessary to produce this low-field orientation dependence. Our data suggest that the magnetic relaxation sites at the glass wall involved here may be the dominant cause of wall relaxation in SEOP cells at any field.