Knowledge Bank

Hydrogen dimers are being studied using a Bomem Fourier transform spectrometer together with long absorption paths (112 m) at very low temperature (20 K) and moderate pressures (10 to 200 torr). Last year at this conference spectra of $(H2)2$ and $(D2)2$ in the regions of the monomer fundamental bands ($3000-5000cm-1$) were presented. New results have now been obtained for $(HD)2$ and for the mixed species $H2-D2$, and $HD-D2$. The region studied has been extended to the monomer first overtone bands at 6000 to $9000cm-1$ and to the pure rotational transitions of $H2$ in the far infrared. Theory has still not developed to the point of being able to use these data to refine the hydrogen intermolecular potential energy surface, but promising work is in progress by J. Schaefer (Garching) and G. Danby (London).