Spectroscopic windows, matrix isolation

The type of apparatus used for spectroscopic studies of metal atoms is shown schematically in Fig. 4. For matrix isolation studies, the window... 

This study was undertaken to isolate and spectroscopically identify the proposed or other intermediates. The technique employed in this work is that of "Matrix-Isolation" where the reactants are allowed to react in a gas-phase kinetic cell and the products are subsequently isolated by an inert gas. The isolated products are then trapped at a cold window (10K) to record the infrared spectra. This technique is well suited to study the reactions in which intermediates or the final products are either unstable or could undergo further chemical reactions. 

The approach to low-temperature spectroscopy that we have chosen to pursue is termed matrix isolation (MI). In MI, the sample is vaporized and then mixed with a large excess of a diluent gas (18,19,20), The gaseous mixture then is deposited on a window at low temperature for spectroscopic examination. The purpose of mixing the sample with the solvent (matrix gas) in the vapor phase is to secure an essentially random distribution of solute molecules, such that each analyte molecule has only matrix gas molecules as nearest neighbors. If this objective is achieved, and if the dilution is sufficiently great that the average distance between any two solute molecules is sufficiently large, then the fluorescence of any one analyte in a complex sample should be essentially unperturbed by the... 

A second method of studying vapor composition is to trap the atoms in a cold, inert material such as frozen argon or xenon. This can be done by employing liquid helium as a coolant (4 K) or special refrigeration units that can go down to below 20 K. A cold window can be employed inside a vacuum chamber, and the vapors coming off the hot metal source can be condensed on the cold window simultaneously with excess argon gas (atoms). In this way the metal particles can be surrounded and trapped in a frozen inert ice. Then the trapped atoms can be analyzed spectroscopically. This method is called matrix isolation spectroscopy and will be discussed in more detail in Section IL.B.2. 

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