EFFECTS OF PRESSURE ON THE OPTICAL-ABSORPTION AND PHOTOLUMINESCENCE OF WOHLER SILOXENE

We have investigated the effect of hydrostatic pressure (P less-than-or-equal-to 5 GPa) oil optical absorption and photoluminescence spectra of Wohler siloxene (Si6O3H6, as prepared) at T = 300 K. The absorption edge energy near 2.75 eV decreases linearly with pressure at a rate of -30+/-3 meV/GPa. For the position of the maximum of the green luminescence band we find a similar pressure coefficient (dE/dP = -24+/-3 meV/GPa). The intensity of the green luminescence shows a reversible decrease with increasing pressure. The pressure dependence of interlayer and intralayer lattice constants has been determined by x-ray powder diffraction. The observed changes in optical transition energies are discussed in the framework of a semiempirical quantum-chemical calculation of the electronic structure of siloxene.