Optical absorption edge in GeSe2

A study of the room and liquid nitrogen temperature absorption edge of GeSe2 has been done using both nonpolarised and polarised light in the spectral range between 2 and 2.8 eV. Direct allowed energy gap values of 2,495 eV and 2,480 eV were obtained for the two directions of polarization E vector parallel a vector and E vector parallel b vector at room temperature and 2,650 eV; 2,700 eV at 77 K respectively. Indirect allowed energy gap values for E Vector parallel a vector and E vector parallel b Vector were 2,315 eV; 2,305 eV at room temperature and 2,520 eV; 2,575 eV at liquid nitrogen temperature respectively. Also the temperature coefficient of these energy gaps has been calculated