Observation of Doubly Spin-Polarized Deuterium by Electron-Spin Resonance

We have studied spin-polarized deuterium, ${\mathrm{D}}_{\downarrow }$, in the temperature range 0.3 to 0.7 K in a field of 40 kG using electron-spin resonance at 114 GHz. The intrinsic rates for recombination of two D atoms to form ${\mathrm{D}}_2$ on the surface of $l-{}_{}{}^4{}_{}{}^{}\mathrm{He}$ have been measured for both the ortho and para channels. The two rates are approximately equal and when extrapolated to zero field are 1600 times greater than the rates for ${\mathrm{H}}_2$ formation. Doubly spin-polarized deuterium, ${\mathrm{D}}_{\downarrow ,↡}$, has been observed for the first time, with nuclear-spin purities > 0.98 and sample lifetimes as long as 1 h.