Microwave absorption by ortho-H2 pairs in solid hydrogen

Measurements of the microwave absorption spectrum of pairs of (J = 1) H 2 molecules at low concentration in (J = 0) solid hydrogen in the frequency ranges 10–26 and 60–90 GHz are reported. Observation of absorptions with coefficients 10 −5 cm −1 is accomplished by a novel calorimetric method. These absorptions result from transitions between energy levels of near neighboring pairs of (J = 1) molecules and assignments are made on the basis of …