The object of the proposed experiment is to definitively locate hydrogen atoms on the extraordinary short B¿B bond by single crystal neutron diffraction method. Because the neutron diffraction analysis is the only method by which the position of the hydrogen atom can be determined experimentally, we would like to use the single crystal diffractometer at ISIS in collaboration with Dr. Matthias Gutmann. Recently, we have synthesized a novel diborane(4) compound (1) supported by the fused-ring bulky groups based on an s-hydrindacene skeleton (Eind groups). Compound 1 is the first example of the double-hydrogen-bridged diborane(4), which would open a new facet of borane chemistry. It is very important to appreciate the precise molecular geometry of 1 including the hydrogen atoms by neutron diffraction analysis experimentally.