Matrix Isolation Method Research Articles

Single Vibronic Level Fluorescence. II. Vapor-Phase Fluorescence Spectra from the Zero-Point Level of B2u1 Benzene and Benzene-d6

Fluorescence spectra have been obtained at 300°K from C6H6 and from C6D6 vapor at 0.1 torr in which all emitting molecules are in the zero-point vibrational level of the B2u1 state. Analysis of the spectra are completed using selection rules appropriate for D6h symmetry of both the ground (1A1g) and excited (1B2u) states. The spectra are compared with the zero-point fluorescence obtained by the conventional method of matrix isolation of benzene at 77°K. The forbidden transitions seen in the latter are absent in isolated molecule gas-phase spectra. The zero-point spectra are also compared with that from a 300°K Boltzmann distribution of B2u1 vibronic levels.

Infrared Spectroscopy at Sub-Ambient Temperatures: III. Molecules and Molecular Fragments within Matrices

The practical and theoretical aspects of infrared spectroscopy of molecules and molecular fragments within matrices at low temperatures are discussed in detail. The following subjects are included in this discussion: the materials used for matrices, the history of the matrix-isolation method of preparation of matrices, unique features of the MIM, problems of the MIM, applications of the MIM, and mathematical models. This paper also discusses pressure and liquid-induced infrared spectra at low temperatures.

Infrared Detection of Diimide, N2H2, and Imidogen, NH, by the Matrix Isolation Method

Hydrazoic acid labeled with deuterium and 15N was photolyzed in solid nitrogen at 20°K. The 15N multiplet splitting positively identifies absorptions of photolysis products as those of trans-N2H2 (at 1286 cm−1), trans-HNND (at 1481 and 1058 cm−1), trans-N2D2 (at 946 cm−1), and cis-N2H2 (at 3074 and 1279 cm−1). The spectrum of trans-N2H2 is in agreement with a planar symmetric structure and the vibrational frequencies are quite close to corresponding vibrations of ethylene. Imidogen, NH, was also observed in both solid argon and in solid nitrogen as another photolysis product. The 15N splitting in the ammonia absorptions shows that the ammonia dimer in solid nitrogen has a cyclic structure.

Density and Expansivity of Solid Xenon

Lattice parameters, densities, and thermal expansion coefficients of polycrystalline xenon are reported for the temperature range from 5.5° to 75°K. A value of 6.1317±0.0005 Å is obtained for the lattice parameter extrapolated to 0°K. Preferred orientation and annealing effects in frozen gases are discussed briefly with reference to matrix isolation methods.

Infrared Detection of the Formyl Radical HCO

The photolysis of HI, DI, HBr, and DBr suspended in solid CO at 20°K is described. The formyl radical, HCO or DCO, is produced, as shown by broad absorptions in the visible spectral region (6695, 6352, 6052, 5789, 5548, 5330, 5102 A) which correspond to absorptions of gaseous HCO. Infrared absorptions of HCO (at 1860 and 1091 cm—1) and of DCO (at 1860 and 856 cm—1) provide a basis for discussing the chemical bonding of this free radical, and for calculating its thermodynamic properties. These experiments, the first infrared detection of a triatomic free radical by the matrix isolation method, depend upon reactivity of the matrix, possibly eliminating difficulties of the cage effect.

Infra-red studies on polyatomic ions isolated in alkali-halide lattices

Different types of matrix isolation methods are described and their uses are discussed. Extensive studies are reported on the vibrational spectra of small polyatomic ions in alkalihalide lattices where they can replace either an anion or a cation. Results are presented for CN −, OH −, NCO −, N 3 −, HF 2 −, NO 3 −, NO 2 −, BH 4 − and NH 4 + and many of their isotopically substituted species. The effect of the environment on the vibrational energy levels of the polyatomic ions is described and the relation Δ( lv i + mv j + nv k = l Δ v i + m Δ v i + n Δ v k is shown to be valid where l, m, n are the vibrational quantum numbers associated with the modes v i , v j , v k present in a combination band and Δ v i is the shift produced in the fundamental v i by the environment. These studies have been carried out over a temperature range from 5°K to 500°K under a resolution of 0·15 cm −1 and the variation of absorption frequencies, intensities and band contours have been obtained.

Recent progress in free radical spectroscopy

New techniques have revolutionized the study of the spectra of free radicals and other unstable molecules. Some of the more important are flash photolysis, matrix isolation methods and paramagnetic resonance. Recent progress is reviewed, particularly in the field of the electronic spectra of complex molecules.

Matrix Isolation Studies: Possible Infrared Spectra of Isomeric Forms of Diazomethane and of Methylene, CH2

The photolysis of diazomethane has been studied by the matrix isolation method. Argon and nitrogen matrices were used at 20°K. There is distinct infrared spectral evidence that unstable species have been detected spectroscopically: the production of stable products is inhibited until diffusion is permitted and a red glow accompanies diffusion. Among the identified products produced during diffusion are ethylene, propylene, methane, and polyethylene. The data suggest that methylene is present as well as a tautomeric structure of diazomethane. One of the absorptions observed at 1362 and 1114 cm—1 could be the bending mode of CH2.

The promise and problems of the matrix isolation method for spectroscopic studies

The promise and problems of the matrix isolation method for spectroscopic studies

Reaction Kinetics by the Matrix Isolation Method: Diffusion in Argon; cis-trans Isomerization of Nitrous Acid

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTReaction Kinetics by the Matrix Isolation Method: Diffusion in Argon; cis-trans Isomerization of Nitrous AcidGeorge C. PimentelCite this: J. Am. Chem. Soc. 1958, 80, 1, 62–64Publication Date (Print):January 1, 1958Publication History Published online1 May 2002Published inissue 1 January 1958https://doi.org/10.1021/ja01534a017RIGHTS & PERMISSIONSArticle Views139Altmetric-Citations28LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (371 KB) Get e-Alerts Get e-Alerts

Matrix Isolation Studies: Infrared Spectra of Intermediate Species in the Photolysis of Hydrazoic Acid

The matrix isolation method has been used to investigate the photolysis of hydrazoic acid (HN3) suspended in xenon, argon, and nitrogen matrices at 20°K. Infrared spectra of the photolyzed material in argon and nitrogen matrices show absorption bands of NH3 and a number of other prominent spectral features that are probably due to unstable molecules, including intermediates in the formation of NH3. In a xenon matrix no new bands are observed on photolysis of HN3 at 20°K, but the presence of the imine radical (NH), or of nitrogen and hydrogen atoms, is inferred from the formation of NH4N3 when the material is warmed to 70°K. The mechanism of photolytic production of radicals in a matrix is examined, and the probable importance of the heat of fusion of the matrix is discussed. The utility of the matrix isolation technique in the infrared study of unstable reaction intermediates is demonstrated.

Spectroscopic Studies of Reactive Molecules by the Matrix Isolation Method

The matrix isolation method for the study of reactive molecules is described. The properties that should be possessed by a material suitable for use as a matrix are discussed with particular reference to spectroscopic investigations. Tests of the method have been conducted with infrared spectroscopic techniques using the free radical NO2 and the hydrogen bonding molecules HBr, HCN, HN3, NH3, and H2O. Xenon, nitrogen, and argon are effective as matrices in isolating these molecules at 20°K with a mole ratio of matrix to active material in the range 100:1 to 500:1. The vibrational frequencies of these molecules isolated in a matrix are nearly the same as the frequencies in the gas phase.