Neon matrices

After the first unsuccessful attempts to record a matrix IR spectrum of the methyl radical, reliable data were obtained by the use of the vacuum pyrolysis method. IR spectra of the radicals CH3 and CD3 frozen in neon matrices were measured among the products of dissociation of CH3I, (CH3)2Hg and CD3I (Snelson, 1970a). The spectra contained three absorptions at 3162 (1 3), 1396 V2) and 617 cm (I l) belonging to the radical CH3 and three bands 2381, 1026 and 463 cm assigned to the radical CD3. Normal coordinate analysis of these intermediates was performed and a valence force field calculated. In accordance with the calculations, methyl radical is a planar species having symmetry >31,. 

Linearity of BeFg was confirmed by electric-deflection studies (1 ) of the vapor and by infrared studies (j ) of matrix-isolated BeF. Infrared absorptions were found near 330 and 1540 cm" in neon matrices, leading to gas-phase estimates of 345 and 1555 cm" (13). The latter absorption was observed (14) at 1520 cm" in the infrared spectra of the vapor at 1000°C. We adopt a compromise of 1530 cm" and use this value in the valence-force-field approximation to estimate 670 cm" for the symmetric stretching mode. 

The electronic levels and vibrational frequencies are those reported by Weltner and McLeod (7). The results were based on a matrix isolation study of Ta02 trapped in argon and neon matrices at 20 K and 4 K, respectively. The infrared spectrum was interpreted to favor a bent molecule in the ground state. Kaufman et al. (8) reported that TaO (g) is bent based on the... 

Figure 24 shows as an example the gas-phase emission and excitation spectra of the radical cation of dimethyldiacetylene from the work of Maier and coworkers and Miller and Bondybey who have pioneered these methods. For direct comparison, the bottom part of Figure 24 represents the same spectra taken in neon matrices (see below). 

The existence of further complexes with M-Ng bonds of this type was deduced on the basis of shifts in the matrix UV/visible spectrum between argon and xenon matrices without recourse either to mixed matrices or neon matrices. (The use of neon matrices should become more frequent now that more efficient closed-cycle coolers are available.) Examples include complexes, Mo(CO)sNg, W(CO)sNg , Cr(CO)3(dfepe)Ng, Mn(dmpe)2(H)Ng, and Re(dmpe)2(H)Ng , and complexes Ru(CO)2(PMe3)2Ng ,... 

Scheme 1. Photochemistry of Cr(CO)g in neon matrices doped with xenon at 6K. (After ref. 5)...

The IR spectra of the N2-HF complex have been reported for neon matrices (in the range 20-8000 cm-1). There was evidence for two distinct sites, e.g. 

Fulara, J. Freivogel, P. Forney, D. Maier, J.P. Electronic absorption spectra of linear carbon chains in neon matrices. III. HC2 +iH. J. Chem. Phys. 1995, 103, 8805-8810. 

BS2 molecules (formed by heating ZnS-B mixtures) may be trapped in neon matrices at 4 Transitions due to theA Il - X Ug and systems may be observed and these, together with matrix- and gas-phase i.r. data, lead to the following molecular constants for BS2. 24 012,... 

A new modification of indium sulphide, y-IngSg, has been prepared by a vapour-phase deposition method. A -Ray, topographical, and electron microscopy studies were carried out and the compound was found to decompose by the loss of sulphur in the electron microscope. The molecular constants of BSg have been determined from a study of the i.r. spectrum obtained at 4 K from the solid, trapped in neon matrices. 

As reported by Lu et the photolysis of methane (and some of its isotopologues) isolated in neon matrices using synchrotron radiation of wavelengths selected in the 120-165 nm range was found to led to the formation of methylidene radicals and The infra-... 

Forney D, Freivogel P, Fulara J, Maier JP. Electronic absorption spectra of cyano-substitut-ed polyacetylene cations in neon matrices. J Chem Phys. 1995 102 1510-4. 

Grutter M, Wyss M, Riaplov E, Maiera JP, Peyerimhoff SD, Hanrath M (1999) Electronic absorption spectra of linear C6, C8 and cyclic CIO, C12 in neon matrices. J Chem Phys 111 7397-7401... 

The full set of molecular constants is available only for E11F2 (Hastie et al., 1971). These data were obtained from the IR spectrum of this compound isolated in different matrices (Ar, Ne, and N2) at 20 K. The V2 frequency was detected in nitrogen and neon matrices (114.5 and 113 cm , respectively). In addition, it was assumed that the vibrational frequencies measured in the argon matrix are the closest to the vibration frequencies of gaseous molecules. In this context, the stretching vibrational frequencies were corrected for the matrix shift (-1-29 cm ), which... 

Ab initio calculations on Cg (Oh, Tj, Csv and D4h) showed that all of these forms are of higher energy than the cyclic form of C4h symmetry vibrational wavenumbers were calculated. Electronic spectra of C2n (n = 4-7) in neon matrices were analysed to determine vibrational states. Thus, for Cg-, Vi (og ) is at 2010 cm , and V2 (ttg ") at 1956 cm . IR spectra were obtained for linear Cn, for n up to 11, in argon and xenon matrices. For Cn, bands were seen at 1946.0 and 1856.7 cm-, for Cio at 2075.4 and 1915.4 cm-. Ab initio calculations of vibrational wavenumbers were reported for isomers of neutral and negatively charged C2o. ... 

Figure 1 Apparatus used for the measurement of absorption spectra of mass-selected cations, anions and neutral radicals in neon matrices.

Figure 2 Electronic absorption spectra of mass-selected polyacetylene cations in 5 K neon matrices.

Figure 3 Absorption spectra of mass-selected carbon anions in neon matrices at 5 K showing several - X electronic transitions.

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