Matrix rare gas

Considerable effort has been expended on Ag atoms and small, silver clusters. Bates and Gruen (10) studied the spectra of sputtered silver atoms (a metal target was bombarded with a beam of 2-keV, argon ions produced with a sputter ion-gun) isolated in D, Ne, and N2. They found that an inverse relationship between Zett of the metal atom and the polarizability of rare-gas matrices (as determined from examination of... 

A number of investigations of the copper-group oxides and dioxygen complexes have been reported. The electronic spectra of CuO, AgO, and AuO were recorded in rare-gas matrices (9), and it was found that the three oxides could be formed effectively by cocondensation of the metal atoms with a dilute, oxygen matrix, followed by near-ultraviolet excitation. The effective wavelengths for CuO or AgO formation were X > 300 nm and for AuO was X > 200 nm. In addition, the laser fluorescence spectrum of CuO in solid Ar has been recorded (97). 

Knight, L. B., Kaup, J. G., Petzold, B., Ayyad, R., Ghanty, T. K., Davidson, E. R., 1999, Electron Spin Resonance Studies of 45Sc170, 89Y170, and 139La170 in Rare Gas Matrices Comparison With Ab Initio Electronic Structure and Nuclear Hyperfine Calculations , J. Chem. Phys., 110, 5658. 

The major relaxation processes of 2P - 2S photoexcited Cu atoms in rare gas matrices are summarized in the following scheme (34). 

The second part of this chapter focuses on actinide chemistry, where we start by describing some triatomic molecules containing a uranium atom, which have been studied both in the gas phase and in rare gas matrices. Most of actinide chemistry occurs, however, in solution, so we then describe actinide ions in solution. The extensive study of the multiple bond between two uranium atoms in the U2 molecule and in other diactinides is then reported. Finally, several examples of inorganic compounds that include U2 as a central unit are presented. 

A simple method for the production and cryogenic trapping of ion-radicals is mentioned. The technique, cold window radical discharge (CWRD), enables the isolation of short-lived species in rare gas matrices, such as p-dichlorobenzene cation-radical. These species are formed within discharge plasmas, close to the trapping surface (Kolos 1995). 

Now concerning the fluorescence, while rare-gas atoms in rare-gas matrices do exhibit fluorescence (see the above reference of Schwentner et al.), NO is, to our knowledge, the sole molecule to exhibit Rydberg fluorescence in the condensed phase. That and the fact that NO has low-lying Rydberg states are the reasons we singled it out as our model system in this study. 

M. Chergui Dimers absorb at -207 nm in rare-gas matrices and excitation of this band does not yield any fluorescence [Chergui et a]., Chem. Phys. Lett. 201,187 (1993)]. Furthermore, our detection is based on the fact that we record the depletion of the fluorescence of one of the A(0, tf") bands due to NO monomers. There is therefore no possibility that NO dimers could interfere with our measurements. 

Pyridazine (1,2-diazine) exhibits a weak fluorescence in solutions at room temperature,73 but no phosphorescence appears in hydrogen and rare gas matrices at 4.2°K. The intersystem crossover was shown to be 103-105 times as slow (at low temperatures) in pyridazine as in pyrazine or pyrimidine.84,85 Very efficient radiationless processes of deactivation must be considered again. 

Unlike the gas-phase measurements, no tunneling has been detected in the IR spectra of malonaladehyde isolated in the rare gas matrices at 15-30 K [Firth et al., 1989]. This disappearance has been attributed to detuning of the potential as a result of weak asymmetric coupling to the environment. 

A number of recent investigations have been concerned with the mobility of heavy atoms in rare gas matrices. Although not directly related to tunneling processes, they are concerned with important fundamental dynamics of atoms and small molecules in low-temperature solids, so we shall briefly review selected examples here. A typical experiment of this type includes the photolytic formation of atoms (see the review by Perutz [1985]) with subsequent detection of the decrease in atom concentrations due to bimolecular recombination. In most cases the rates are diffusion limited, and the temperature dependences are characteristic of thermally activated transfer. 

The half-life of 181W has been re-investigated and a value of 120.95 + 0.02 days determined, which differs significantly from the currently accepted value 272 The u.v. absorption spectra of molybdenum atoms isolated in rare-gas matrices at 14 K have been correlated with similar gas-phase spectral data and assigned in spherical symmetry. Diffusion of the metal atoms in an Ar matrix was also studied and some tentative evidence obtained for dimer formation.273 The standard heat of vapourization of molybdenum has been determined274 as 689.3 kJ (g atom)-1. 

The proton transfer reaction has been also studied in rare gas matrices, showing some discrepancies with the gas phase (Brucker and Kelley 1989a,b Crepin and Tramer 1991) in 1- and 2-naphthol with ammonia, the AH B — A -HB + transition takes place for AH (NH3) /Ar matrix-embedded clusters with n > 3 (Brucker and Kelley 1989a,b). 

The optical absorption, fluorescence and photochemical properties of Ag, provide clear evidence for the occurrence of two distinct forms of Ag in each of the three rare gas matrices (4,8,9). This observation shows that the matrix environment can act to stabilize distinct isomeric forms of this species. It appears that a common form of Ag° is produced during matrix formation in Ar, Kr and Xe and a structurally different yet common form of Ag" is produced by photoinduced aggregation of Ag° atoms in Ar matrices and photoisomerization of Ag, in Kr and Xe matrices. The results available for Ag ,Ag° in rare gas matrices are summarized below ... 

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