Derivation of the density of states and distribution functions for two-level systems in glasses

Abstract

A formalism for calculating the density of states (DOS) function for tunneling systems in amorphous materials is described.Gaussian distribution functions for the asymmetry (A) and the tunneling parameter (X) are employed. It is shown that over a broad energy range ( E << hwo) the DOS function is an increasing function of energy proportional to EL@ with 0.3 5 perf

Nonphotochemical hole burning and dispersive kinetics in amorphous solids

“…These and other results are theoretically analyzed using the distribution function, f (R) , proposed by Jankowiak et al [14,30] and by Jankowiak and Small [18]. This function is based on the assumption that a Gaussian distribution for the tunnel parameter A is physically reasonable [9,31]. In all cases this distribution function is found to provide a satisfactory description of the dispersive kinetics.…”

“…Ignorance of the microscopic structures of the TLS has led to considerable flexibility in the selection of phenomenological distribution functions for A and A [9].…”

“…Since this value has been utilized in earlier work [5,9,14,29,30,40,41] Elschner and Bâssler [13,15], Jankowiak and Small [18] and Jankowiak et al [9,12,30] have argued that a Gaussian distribution function for A is physically reasonable. shown that [14] (%)"…”

“…Recently, Elschner and Bassler [62] were first used to obtain an analytic expression for the TLS density of states p(E), where E is the tunnel state splitting (E^ = + A^) [9]. Following that it was shown that they lead to more accurate configurâtional averaging for the optical dephasing frequency [30].…”

Spectroscopy of amorphous substances with molecular structure

“…Âûøå óïîìèíàëîñü, ÷òî îäíîé èç ìîäåëåé ÄÓÑ ðàññìàò-ðèâàëàñü ìîäåëü êâàçèaeèäêîãî êëàñòåðà ìîëåêóë [47].  ñâîþ î÷åðåäü, íåîäíîðîäíîñòü êâàçèaeèäêîñòíîé ñòðóêòóðû ïðèâîäèò ê ñóùåñòâîâàíèþ íàáîðà ÄÓÑ, îòëè÷àþùèõñÿ çíà÷åíèÿìè ïàðàìåòðîâ ∆ è λ. Íà îñíîâà-íèè òîãî, ÷òî ñòðóêòóðíûå ïàðàìåòðû óïàêîâêè ìîëåêóë, êàê îêàçàëîñü [19], ïîäâåðaeåíû ãàóññîâîìó ðàñïðåäåëåíèþ, áûëî ïðåäïîëîaeåíî, ÷òî è ïàðàìåòðû òóííåëîíîâ ∆ è λ òàêaeå ðàñïðåäåëåíû ïî Ãàóññó [68,70], ñëåäñòâèåì ÷åãî ÿâëÿåòñÿ ÷àñòîòíàÿ çàâèñèìîñòü ïëîòíîñòè ýíåðãèè òóííåëüíûõ ñîñòîÿíèé â âèäå Òàêèì îáðàçîì, ââåäåíèå ÄÓÑ åñòåñòâåííûì îáðàçîì îáúÿñíÿåò ñó-ùåñòâîâàíèå ìåäëåííîãî ðåîðèåíòàöèîííîãî äâèaeåíèÿ, âûçûâàþùåãî ÊÓÐ â ñïåêòðàõ ÍÍÐÍ è ÊÐÑ. Õàðàêòåð ýòèõ ñîñòîÿíèé äåëàåò ÊÓÐ íåéòðîíîâ [7174] è ôîòîíîâ [58] äåéñòâèòåëüíî óíèâåðñàëüíûì ñâîé-ñòâîì àìîðôèêîâ.…”