<title>Optical properties of a near-surface crystal layer with color centers</title>

Abstract

ABSTRACT A role of different factors, influencing on intensity of color centers formation on structural defects of a crystals surface layerand change of its optical properties at the moment of irradiation by vacuum ultraviolet radiation, are discussed.Keywords: point defect, color centers, near-surface layer, attenuated total reflection spectroscopy, dipole moment, opticalconstants. 1. INTRODUCTION The alkali-halide and alkali-earth crystals (AHCS and AECS) are widly used as constructing materials in optical instrumentmaking. However their spectral properties are sensitive to alteration of regular spatial arrangement of ions in a crystal lattice.Appearance in a crystal cell of additional or impurity atom, a ion, formation of a vacancy are the causes of local changing ofelectrostatic field in a crystal lattice. There are reasons for formation of color centers (CC) on structural crystal defects, whichare selective absorbing in ultra-violet and visible ranges [1].The different optical process accompanying the CC formation and its decay are effectively used. The crystals with CC applyat the creation of lasers, radiation indicators, optical memory cells for keeping of information, including as mediums to a recordof holograms. But the predisposition of the crystals to CC formation has a negative effect during exploitation of crystallineoptical elements, when materials must preserve high transparency at long time.The CC accumulation is inevitably even in crystals, which have been grow by modem methods with a minimum of impuritiesconcentration and defects. After machining treatment of a crystal of a lattice structure is violated and the material surface issupersaturated by point defects, which, interacting with external radiation, under certain condition can turn into CC.