Self organization and low frequency Raman scattering in quartz glasses irradiated by fast neutrons

In all investigated glasses materials in low frequency region of the IR absorption and Raman scattering spectra intensive and sufficiently broad band with maximum within ∼10-100 cm-1 is observed. The availability of such band is a typical trait of low frequency spectra of amorphous materials and spectroscopic characteristics of this observed low frequency peak in glasses are similar to the spectra of liquids and liquid crystals. In this work the influence of fast neutrons (from 2.5·1015 to 2.2·1020 cm-2) on location of low frequency peak in quartz glass was investigated with accidental impurities (Ca, Al, Ba, Sb, Pb, Mn, B, Na, Zn), in which summary maintenance of impurities was (1013-10-1) mass %). Spectral from of low frequency Raman scattering peak is identical in all glasses independently from their chemical composition. It is discovered that the frequency and amplitude of boson peak increase with increasing of irradiation dose. Maximum of peak is displaced from 54 to 72 cm-1 depending on irradiation dose, but amplitude is increased up to 1.5 times. The increasing of glass density and velocity of acoustic waves propagation are observed. Depending on E-centre (28Si3+) concentration under irradiation dose at first a gradual growth, and then saturation of these centres is observed. The increasing of concentration of centres correlates with the growth of intensity of narrow Raman line 606 cm-1, connected to oxygen atoms' vibrations on the clusters surface. The irradiation by fast neutron lead to the changing degree of self organization of phase correlation in glasses. It leads to the rising of internal field of phase structure, and consequently, to the changing of wave vector of phase structure, which is displayed in the shift of frequency of boson peak. The changing of self organization degree influences the macroscopic parameters of medium and it is displayed in the changing of glass density and velocity of acoustic waves propagation. The increasing of internal field of phase structure is equivalent to the changing of distribution of energetic states because of the changing of self organization degree. This process leads to the changing of density of fluctuation transitions between hierarchies of energies' states, which is displayed in the growth of E' - centres concentration and Raman line intensity. In our opinion the nature of boson peak is formed by more sensible processes in medium, just by phase correlation radius, which plays the main role in the forming of macroscopic parameters of medium. Frequency distribution of boson peak displays the internal field distribution of non-regulated medium phase structure