Nonradiative Relaxation of Excited Vibrational States of Solid Hydrogen

The vibrational-rotational relaxation of molecular hydrogen in the solid phase is measured by the transient optothermal lensing effect. We have obtained the relaxation rates for the first, second, and third vibrational levels leading to $k_v\approx v\times 1.89\times {10}^5$ ${\sec }^{-1\mathrm{}}$, where $v$ is the vibrational quantum number. This relationship is consistent with the energy-gap law and is a manifestation of the multiphonon relaxation mechanism.