IR spectroscopy of fast neutron irradiated diamonds

The paper presents the results of a study of the effect of irradiation with fast neutrons and subsequent annealing on the IR absorption spectra (range 400-11000 cm^-1 ) of diamonds deposited from the gas phase. It is shown that radiation damage to diamond greatly enhances absorption in the region of one-phonon transitions. The transformations of the IR absorption spectra in the range 3000-11000 cm^-1 , in which electron-vibrational transitions in radiation defects in diamond are manifested, have been studied in detail. It is shown that the most intense absorption band in the IR spectra of diamonds irradiated with neutrons with fluences of (1-3)×10¹⁸ cm^-1 with a maximum near 9300 cm^-1 is a superposition of two bands at 9280 and 9320 cm^-1. The processes of formation and annealing of multi-vacancy nitrogen-free centers with zero-phonon lines at 4065 and 4112 cm^-1, characteristic of natural and synthetic diamonds of brown color, have been investigated. (authors)