“…The details of the sample preparation and optical properties of this glass have been reported earlier [3,4]. The sample was mounted in an ordinary T-controlled (5-300 K) liquid-helium cryostat for measurements at normal P or in a pressure cell placed inside a special T-controlled (down to 4.7 K) liquidhelium cryostat for measurements at high hydrostatic P. In that case we used our high-P low-T system [5], employing compressed gaseous or solidified helium as the P-transmitting medium.…”