Radiation-induced formation of stable charge centers in rare-gas solids Elena V. Savchenko a, * ,1 , Alexander N. Ogurtsov a,1 , Oleg N. Grigorashchenko a,2 , Martin Beyer b , Martin Lorenz b , Andreas Lammers b , Vladimir E. Bondybey b a Verkin Institute for Low Temperature Physics and Engineering, Kharkov 310164, Ukraine b Institut f ur Physikalische und Theoretische Chemie der TU M unchen, 85747 Garching, Germany Abstract Molecular ion centers (XeAr)  in solid Ne were produced by deposition of an ion-containing gas on a cooled substrate. Laser-induced ¯uorescence (LIF) and excitation yield were studied in the range of transitions between the ground state of the ionic centers and the lower excited states related to the 2 P 1=2 , 2 P 3=2 limits of Xe  . The ¯uorescence of (XeAr)  exhibits a vibrational structure with a spacing between the peaks of the ¯uorescence progression of about x e  11:1 meV. Ó 2000 Elsevier Science B.V. All rights reserved. PACS: 33.15e; 72.20Jv; 78.55Hx Keywords: Rare-gas solids; Molecular ions; Matrix isolation; Fluorescence 1. Introduction Charge carriers in insulators, their stability and dynamics are a topic of considerable importance in radiation physics, material science and chemistry. The study of the problem in rare-gas solids (RGS) ± the widest band gap insulators ± has an advan- tage because the lattice rearrangement induced by phonon interaction with electronic excitation is not obscured by interatomic interaction which is extremely weak in these solids. The formation of ionic centers in RGS is closely related to the fun- damental problem of hole self-trapping [1], and is of special interest in view of the prominent role of holes in radiation-induced phenomena, charge transport, dosimetry and photochemistry in cryo- genic solids. Charge centers in RGS were tested by the thermoluminescence method [2±4]. A new ex- perimental approach [5] to study ionic centers was employed: the investigation of `frozen plasma'. The samples were grown from discharge so that the ionic species were embedded into the growing matrix. It was found [6] that the con®guration and the electronic structure of intrinsic ionic centers are identical with those of self-trapped holes, which were generated in situ with vacuum ultra- violet ionizing radiation. The intrinsic ionic centers Nuclear Instruments and Methods in Physics Research B 166±167 (2000) 47±50 www.elsevier.nl/locate/nimb * Corresponding author. Tel.: +380-572-300336; fax: +380- 572-322370. E-mail address: savchenko@ch.tum.de (E.V. Savchenko). 1 Partially supported by DFG and BMBF, Germany. 2 Partially supported by BMBF, Germany. 0168-583X/00/$ - see front matter Ó 2000 Elsevier Science B.V. All rights reserved. PII: S 0 1 6 8 - 5 8 3 X ( 9 9 ) 0 0 6 4 2 - 4