5314027789

POSTER SESSION. H52

high resolution excitation of molecular lumines-

CENCE FROM RARE GAS SOLIDS

ALEXANDER N. OGURTSOY. O. N. GRIGORASHCHENKO,

E. V. SAVCHENKO, Verkin Institute for Low Temperaturę Physics &

Engineering, 310164 Kharkou, Ukrainę.

Rare Gas Solids (RGS) constitute a group of insulating materials which exhibit the strong molecular features łn luminescence as a result of radiative decay of intrinsic molecular neutral RJ (self-trapped excitons) and ionic Rj (self-trapped holes) centers. The luminescence spectrum of molecular centers consists of three well-defined continua. The first one (so-called W-band) is the most short-wavelength continuum. It corresponds to the ‘•³Eu^(l’⁾ -¥ ‘E+ “hot” transitions in emission of dense rare gases. The second continuum (so-called Af-band) is the most prominent feature in luminescence from solid Ar, Kr and Xe. It is formed by the ^l,3EJ -> *£+ transitions in quasi-excimers RJ- The origin of the third continuum (so-called H-band) is not quite elear. Recent cathodo-, photo- and ther-moluminescence studies of the third continuum in near UV and VUV luminescence from Rare Gas Solids undoubtedly certify that the //-band is formed as a result of radiative decay of intrinsic ionic molecular centers⁰. The most appropriate configuration of such a center is the trapped or self-trapped hole "dressed" into cxciton [R% *), but the probability of participation of double charged dimers (Rf ⁺ )» or even trimers (Rj*) in the H-band formation should not be excluded.

In recent measurements of molecular luminescence from RGS under high resolution ex-ritation by synchrotron radiation, using a Computer deconvolution of spectra obtained, we have determined the internal structure of molecular luminescence bands. Comparison with previous data on cathodo- photo- and thermołuminescence* allowed us to separatc the next steps in luminescence band formation: 1) free exciton ionization accompanied by trapping of charge carriers: R*_x -» Rf +c"; 2) “dressing” of trapped hole by ex-citon with subsequent 11-band emission: Rj + RJ* -» Rj* R⁺ + R + hi/(H); 3) bulk recombination of trapped hole with electron followed by exciton self-trapping and Af-band emission: ^bua R₂^f + e"-ł ^“^RjR + R -f/n/(M); 4) surface recombination of trapped hole with electron followed by desorption of excimers and W-band emission: ^Aur^R.J + e" —» ^drsorbR^ —> R + R + /iiy(W). In the excitation spectrum of VF-band of solid Ar all fine dctails of excitonic bands structure, including States of surface excitons, were detected.

°A. N. Ogurtsov. E. V. Savchenko, J. Becker, M. Runne, G. Ziinmerer, J. Luminesc. in press (1998); O. N Grigorashchenko, S. A. Gubin, A. N. Ogurtsov, J. Electron. Spectrosc. 79, 107 (1996).

^hA. N. Ogurtsov, E. V Savchcnko, O. N. Grigorashchenko, S. A. Gubin, I. Ya. Fugol, Low. Temp. Phys. 22. 922 (1996); E. V. Savchenko, A. N. Ogurtsov, O. N. Grigorashchenko, Phys. Sol. State, in press (1998).