James P. Riehl

Determination of atomic oxygen density and temperature of the thermosphere by remote sensing

Abstract Measurement of emission from the Earths atmosphere in the far infrared due to transitions between fine structure levels of the ground state ( 3 P) of atomic oxygen at 63 μm ( 3 P 1 → 3 P 2 ) and 147 μm ( 3 P 0 → 3 P 1 ) is proposed. These magnetic-dipole allowed transitions with long radiative lifetimes (∼ 3.2 h for the 63 μm transition and ∼ 16.3 h for the 147 μm transition) are assumed to be in equilibrium with the local translational temperature. A one-dimensional onion-peel inversion of the limb emissions at 63 and 147 μm from a model atmosphere is shown to yield reasonable results for both the temperature and atomic oxygen density in the 90–250 km altitude range.

Applications of circularly polarized luminescence spectroscopy to biochemical systems

Abstract Circularly polarized luminescence from Tb(III) bound to the protein calmodulin at micromolar concentrations is reported. The CPL is monitored as equivalents of the lanthanide are added to the protein solution. Maximum optical activity is obtained when two equivalents are added. These results can be interpreted in terms of conformational changes of the protein.

Circularly polarized luminescence spectroscopy of mixed-ligand complexes of europium(III) with 2,6-pyridine-dicarboxyclic acid and L-malic acid

Abstract Circularly polarized luminescence (CPL) from solutions of Eu(III), 2,6-pyridine carboxylic acid (dipicolinic acid, DPA ), and L-malic acid (L-mal) at differing concentration ratios have been measured. The magnitude and sign of the CPL under varying excitation polarizations are quite different indicating that the source of the emission under these conditions is not the same. Comparison of the CPL observed for a solution in which DPA and L-malic acid are present to that of pure Eu: DPA and Eu:L-mal under identical conditions suggests that most of the emission in the mixed-ligand system occurs from Eu( DPA ) 3 3− , and not from a species containing two DPA ligands and one L-mal.

The polarization of pure electric quadrupole transitions in the electronic spectra of molecules

The polarization properties of electric quadrupole contributions to molecular electronic transitions are examined theoretically. Possible manifestations of these electric quadrupole contributions in various types of polarized absorption and emission spectra are considered in detail. The types of polarized spectra considered are circular dichroism (CD), linear dichroism (LD), circularly polarized luminescence (CPL), linearly polarized luminescence (LPL), magnetic circular dichroism (MCD), magnetic linear dichroism (MLD), magnetic circularly polarized luminescence (MCPL), and magnetic linearly polarized luminescence (MLPL). In emission the possible effects of photoselection and reorientational relaxation are investigated. Calculations are presented for the A2g↔T1g transitions of octahedral (Oh) systems and for the Σ+g↔Πu, Πg, and Δg transitions of homonuclear diatomic molecules (D∞h) under a variety of conditions. The identification and characterization of pure electric quadrupole (electronic) transitions u...

The dynamics of vibrational transitions in molecules: A classical model

The absorption of infrared radiation by molecules is examined by comparison with a classical one‐dimensional 3‐particle model. The equations of motion for this system are solved while it interacts with a classical electromagnetic wave. It is shown that direct ’’electron’’–radiation and nuclei–radiation interactions contribute approximately equally to the absorption process.

Recovery of atomic oxygen density and temperature of the thermosphere by numerical inversion of simulated infrared radiance data with gaussian noise

Abstract It is demonstrated that the recovery of oxygen atom density and temperature atmospheric profiles can be obtained from numerical inversion of simulated limb-look radiance from the two atomic oxygen far infra-red fine-structure transitions at 63 μ m ( 3 P 1 → 3 P 2 ) and 128 μ m ( 3 P 0 → 3 P 1 ) . The inversion of simulated radiance data with reasonable estimates of noise is possible if both the integrated radiance and line-center radiance are available for both transitions. In order for the recovery of the atmospheric parameters to be successful down to regions of high oxygen atom density (100 km), it is necessary to smooth the noisy radiance data prior to application of a modified Gauss-Newton algorithm. Best results were obtained when a combination of cubic spline and optimal filtering smoothing techniques were used.

Time-dependent concentration depolarization: A Monte Carlo study

Abstract The phenomenon of time-dependent concentration depolarization is examined by a Monte Carlo procedure. The method described is general and versatile, and allows one to arbitrarily choose absorption and emission molecular polarizations, energy transfer mechanisms, and radial and orientational distribution functions. Comparison is made with recent theoretical results on time-dependent depolarization, and with experimental results on the “steady-state” depolarization of the phosphorescence of phenanthrene-d10. Good agreement is obtained for a wide range of concentrations.