Showing papers by "Lester Andrews published in 1972"

Raman Spectra of the Products of Na and K Atom Argon Matrix Reactions with O2 Molecules

Abstract: Raman spectra of samples of sodium and potassium atoms codeposited at 16°K with oxygen molecules at high dilution in argon showed strong bands at 1094 and 1108 cm−1, respectively, which are assigned to the superoxide fundamentals in the Na+O2− and K+O2− molecules. These features were split into triplets using 16O2, 16O18O, 18O2 samples, which indicates isosceles triangular structures; absence of M+–O2− interionic modes confirms the ionic model for the alkali superoxide molecules. Infrared bands at 1079 and 1097–1104 cm−1 in Na and K atom −O2 reactions, respectively, are assigned to the dimeric species (M+O2−)2. The symmetric metal‐oxygen mode for O2KO2 was observed in the Raman at 305 cm−1, inferring more covalent character in the metal oxygen bonding in this species than in the alkali superoxides.

Raman and Infrared Spectra of LiO2 in Oxygen Matrices

Abstract: The Raman spectrum of the LiO2 molecule has been observed from samples of oxygen codeposited with lithium atoms at 15°K. An intense band at 1093 cm−1 in the Raman spectrum exhibited appropriate oxygen isotopic shifts for assignment to the symmetric oxygen‐oxygen vibrational mode. Experiments using a 16O2, 16O18O, 18O2 sample produced a triplet indicating equivalent oxygen atoms in the LiO2 molecule. Lithium oxygen vibrations, which were very intense bands in the infrared spectrum, were not detected in the Raman spectrum. The observed Raman intensities strongly support the ionic model for LiO2 proposed earlier. The experimental apparatus and techniques for laser‐Raman matrix‐isolation spectroscopy are described.

Argon Matrix Raman Spectra of Oxygen Difluoride and the Oxygen Fluoride Free Radical

Abstract: The argon matrix Raman spectra of oxygen difluoride and oxygen‐18 difluoride at 16°K have been observed; frequencies within one wavenumber of analogous infrared studies were measured. Laser photo‐detachment of fluorine atoms has provided significant yields of the OF and 18OF free radicals; the Raman observations confirm the earlier infrared work. Temperature cycling operations and depolarization ratio measurements provide aid in identifying new chemical species and making vibrational assignments.

Computer Time Averaging of Laser Raman Spectra for Matrix-Isolated Species

Abstract: With the recent development of commercially available laser-Raman spectrometers, many previously impossible types of experiments are now being performed. One of these areas of research is the laser-Raman spectroscopy of matrix-isolated samples.1–7 In this application, relatively weak signals (from the dilute sample of interest) are measured with large amounts of background scatter from the matrix material. Thus, background signals as large as 1 × 10−8 A must be suppressed while the peak signals of interest may be as small as ~0.1 × 10−9 A; under these conditions the signal-to-noise ratio becomes the limiting factor in obtaining useful spectra.