(Inset) The face-centered-cubic (fcc) based structure of the newly discovered compound , in which 8 out of 9 atoms are hydrogen. The blue spheres indicate units (which may not have definite orientations) and the red spheres represent pairs (with also as yet unknown orientational physics). (Raman spectrum, right) at and an average electron density greater than that of silane shows excitations characteristic of molecular hydrogen () and plausibly connected with the placement of the pairs. (Spectrum, left) The deuterated system again shows excitations characteristic of the molecule. (Spectrum, middle) The presence of the mixed isotope pair means that there is time dependent migration of from the blue regions into the red regions (and can be migrated into the blue regions).