Nelson McAvoy

Broadband CO 2 Laser Coupling Modulation

The application of coupling modulation is described for achieving a 110-MHz bandwidth using CO2 lasers and GaAs electrooptic crystals. Coupling modulation is a technique that has no bandwidth limitations and allows the modulation bandwidth to exceed that of the laser resonator.

A stable submillimeter laser local oscillator for heterodyne radiometry and spectroscopy

A submillimeter laser with off-axis pump beam injection is described. This design concept achieves complete isolation of the pump laser with respect to the pump radiation reflected from the smm resonator. Active line independent stabilization of the pump laser is obtained by the use of an external tunable etalon as a frequency reference. The smm output power is constant to within 4% over periods of hours. Mean frequency drifts of less than 2 parts in 108 per minute were measured by mixing with very high harmonics of an X-band synthesizer in a planar Schottky diode.

Spectra and quantum states of europium β-diketone chelates in polymethylmethacrylate

Abstract An analysis of the absorption spectra of different Eu β-diketone chelates led to a detailed spectroscopic investigation of Eu tris (4,4,4-trifluoro-1,2 thienyl-1,3 butanedione) chelate dissolved in polymethylmethacrylate and other hosts, at different temperatures and concentrations. The mechanism responsible for the line fluorescence is attributed to an intramolecular energy transfer from the triplet states of the organic chelate to the 5 D 0 and 5 D 1 resonance energy levels of the central europium ion. The concentration, temperature and host dependent fluorescence spectrum of Eu chelate have been investigated and interpreted. The absorption and phosphorescence spectra of the identical gadolinium chelate in different hosts were related to the overall transfer mechanism and the lowest-lying triplet states. The “molecular field splitting” effects are observed at low temperatures for the 7 F 0 → 5 D 2 transition and interpreted based on structural criteria. The intramolecular energy transfer has been tentatively formulated based on the admixture of the biradical triplet state of the chelate with the emitting levels of the europium ion.

Analysis of Fluorescence Spectra of Rare‐Earth Chelates. II. Dipyridyl Complexes of Europic Chloride

The emission spectra of two dipyridyl complexes of EuCl3 were analyzed in detail treating the ligand field as a perturbation on the free‐ion levels. The ligand‐field parameters were calculated from the splitting in the 7F1 and 7F2 levels of the Eu3 + ion without assuming a known molecular geometry and the model suggested by these parameters is discussed. In addition, the ligand‐field parameters are used to calculate interatomic distances and to compare the coordinative properties of water and dipyridyl ligands. The method developed for deriving and verifying the geometrical arrangement and interatomic distances from fluorescence spectra proves to be a powerful tool.

433 Micron Laser Heterodyne Observations Of Galactic CO From Mauna Kea

A submillimeter heterodyne radiometer, developed for astronomical applications, uses an optically pumped laser local oscillator and a quasi-optical Schottky diode mixer. The resultant telescope-mounted system, which has a noise temperature less than 4000 K (double sideband) and high frequency and spatial resolution, has been used to detect the J = 6 -4- 5 rotational transition of carbon monoxide at 434 micrometers in the Orion molecular cloud. The measurements, when compared with previous millimeter-wave data, indicate that the broad carbon monoxide emission feature is produced by an optically thin gas whose temperature exceeds 180 K.

Fluorescence Spectra of Homogeneous and Mixed Europium Complexes

High-resolution emission spectra of several europium complexes with β-diketones, dipyridyl, and phenanthroline have been examined at 77°K in microcrystals. The Stark splitting of the 7F levels in the ground multiplet and the relative intensities of the individual 5D0→7F transitions can be used for theoretical correlation with the ligand field parameters, transition probabilities, molecular structure, and Eu-ligand bonding. The fluorescence spectra of the bis-aqua, tris, tris-aqua, tetrakis, and mixed chelates with the bidentate ligands are discussed in relation to molecular configuration.

Liquid laser cavities

New liquid laser cavities have been developed in which the capillary cell is almost three times longer than the previously reported piston-type cells. These new cavities have plenum chambers at the ends of the cell which are terminated in transparent optical flats. The design allows the use of external confocal or plane mirrors and an accurate alignment. By use of these cavities it has been demonstrated that several new europium chelates and, for the first time, a terbium chelate can perform laser action in solution at room temperature.

Detection Of Upper Atmospheric Constituents Using Submillimeter Wave (SMMW) Heterodyne Radiometry

Typical of new applications of the rapidly developing submillimeter wave (SMMW) technology is the detection and sounding of upper atmospheric constituents. Before discussing this application it is appropriate to review coherent receiver concepts as they pass from the microwaves and mm-waves through the infrared. This is necessary because SMMAI is being approached from both ends of the spectrum conceptually and with experimental apparatus.

Organic cation effects on the internal Stark splitting in the fluorescence spectra of tetrakis(dibenzoylmethido)europates(III)

A study has been made of the changes in the internal Stark splitting observed in the fluorescence spectra of tetrakis(dibenzoylmethido)europates(III) upon replacing a quaternary Et4N+ organic cation with other tertiary, secondary, and primary ammonium ions. Treating the molecular field as a perturbation on the free-ion levels, the ligand-field parameters have been calculated and their values are discussed in terms of molecular configuration.