Rapid Decay Mechanisms for Bulk Spin-Aligned Atomic Hydrogen atT=0K in Large Magnetic Fields

Solid spin-aligned atomic hydrogen is shown to be unstable against spontaneous magnon creation due to electronic dipole-dipole and hyperfine interactions even at $T=0\mathrm{}$ K for magnetic fields less than $H_c\approx \frac{7.3\tilde{J}}{{\mu }_e}$, where $\tilde{J}$ is the motionally averaged exchange interaction. For an fcc crystal at 50 ${\mathrm{cm}}^3$/mole, $H_c\approx {10}^6$ G. Similar considerations apply to the fluid state where the relevant parameter is again $\tilde{J}$ which is proportional to the density in the low-density limit.