Detection of clustered H(2) at 4.2K.

A special calorimeter is described which is capable of detecting molecular hydrogen trapped in solid material. It takes advantage of the energy released by the slow otho-para conversion of H(2) after rapid cooling from room temperature to 4.2K. The technique is simple, quantitative, and non-destructive, and can be used on any non-magnetic host with a sensitive of ~10 (17)H(2), or typically 1 ppm for a 1-cm(3) sample. The rate of decay also gives information about the local configuration of the H(2). Data are presented for H(2) clustered in 50angstroms- dia. microvoids in films of electroless deposited Cu.