Measurement of Slow Vibrational Relaxation and Fast Vibrational Energy Transfer in SolidN2

The decay rates of the vibrational levels $v=3\mathrm{}$ to $v=13\mathrm{}$ in ground-state ${\mathrm{N}}_2$ have been measured in solid nitrogen between 4.2 and 18 K. In N-atom-doped but otherwise highly purified solid ${\mathrm{N}}_2$, the vibrational relaxation rates are found to be fitted by the expression $P_{v\to v-1\mathrm{}}=A_v+B_v\exp (-\frac{\Delta E_v}{\mathrm{kT}})$. The rate $A_v\cong v\times \left(1\mathrm{} invsec\right)$ is interpreted as the multiphonon creation rate in the $v\to v-1\mathrm{}$ relaxation, while $B_v\cong 6\times {10}^8$ ${\sec }^{-1\mathrm{}}$ near $v=10\mathrm{}$ describes the intermolecular transfer of a vibrational quantum, ${\mathrm{N}}_2\mathrm{}\left(v\right)+{\mathrm{N}}_2\mathrm{}\left(0\right)\mathrm{}\to {\mathrm{N}}_2\mathrm{}(v-1\mathrm{})+{\mathrm{N}}_2\mathrm{}\left(1\right)\mathrm{}$, with energy mismatch $\Delta E_v=E_1-E_0-E_v+E_{v-1\mathrm{}}$.