The rotational line of hydrogen is very clearly measured with TOSCA. For the past few years I have noticed that the changes in the position of the rotational line do not follow the expected behaviour unless there is very little interaction between the molecule and the surface. In some metal oxides the results seem to suggest that the changes are not due to an orientational potential but can be better explained by an elongation of the H-H bond. However, the results from the INS spectroscopy are an indirect measure of such effect and do not prove it. If there is an elongation of the molecule while still preserving the quantum properties of the rotational wavefunction, it may be a very important result, since this phenomena has been observed in TOSCA on quite few systems that are well know catalyst supports.