Frederick G. Smith

Computation of electric dipole matrix elements for hydrogen fluoride

Abstract The electric dipole matrix elements of hydrogen fluoride have been calculated by numerical integration for transitions involving large quantum numbers υ, J. Overtones have been included through Δυ = 5. Molecular wave functions obtained by numerical integration of the Schrodinger equation were used. The influence of the mechanical motion on the matrix elements has been determined for Morse and Rydberg-Klein-Rees (RKR) potential functions. The influence of the electric dipole-moment function approximations has been investigated by a comparison of matrix elements obtained with approximations having the form of a truncated polynomial and a wave-function expansion. The inaccuracies in the matrix elements caused by uncertainties in the dipole-moment coefficients have been investigated.

Strengths and Collision Broadened Widths in the Second Overtone Band of Hydrogen Fluoride

Individual line strengths and self‐broadened half‐widths have been measured in the second overtone band of hydrogen fluoride. The electric dipole matrix element for the band has been determined from the measured strengths. Its value is: 〈 3|μ(r)|0〉exp=+1.628× 10−21 esu· cm. The m dependence of the measured half‐widths agree with the Anderson theory of collision broadening if off resonant collisions are taken into account.

Passive target detection using polarized components of infrared signatures

The potential of infrared polarized signature components for suppressing background clutter and enhancing the detection of dim targets has been investigated. An imaging infrared polarimeter has been built, field experiments have been conducted, and measured results have been compared with theoretical predictions. A description of the measuring instrument, samples of empirical findings, and comparisons with simple theoretical predictions are presented.

Dipole moment function and vibration-rotation matrix elements of HCl35 and DCl35☆

Abstract The infrared intensity measurements and molecular beam electric resonance dipole moment measurements for HCl and DCl have been reviewed. A method not previously exploited is used to determine infrared matrix elements from the electric resonance dipole moment measurements. A ‘best’ set of matrix element values was selected for HCl and from these the Mi-coefficients of a polynomial dipole moment approximation were determined; M0 = 1.0935±0.0007 D, M 1 = 0.947±0.023 D/ A , M 2 = 0.015±0.041 D/ A 2 , M 3 = -0.814± 0.116 D/ A 3 . Calculations using this dipole moment function for both HCl and DCl are shown to give good agreement with available band strength and vibration-rotation interaction factor measurements. RKR potentials are also calculated for both molecules.

Water vapor continuum absorption in the 3.5–4.0-μm region

Measurements of water vapor continuum absorption in the 3.5-4.0-microm region are presented. The measurements were made with both long-path absorption cell and spectrophone systems. A deuterium fluoride grating tunable laser was the ir source. Measurements were made at 23 degrees C and 65 degrees C with 14.3 Torr and 65 Torr of water vapor, respectively, buffered to 760-Torr total pressure by an 80/20 mixture of N(2)/O(2). Both natural water and a special sample of deuterium depleted water (one-fiftieth the normal concentration) were used. The 65 degrees C results agree with previous measurements by other workers. The 23 degrees C results indicate a continuum absorption at this temperature about a factor of 2 larger than expected based on the extrapolation scheme and high-temperature data (>/=65 degrees C) of others.

Broadening of hydrogen fluoride lines by H2, D2, and N2

Foreign gas broadening of the vibration‐rotation lines in the first overtone band of hydrogen fluoride have been investigated. Linewidths broadened by N2, H2, and D2 have been measured for 15 lines in the band at a resolution of approximately 0.1 cm−1. Comparison of the measured widths with predictions based on the Anderson theory show good agreement only for N2 broadening of the lower J transitions. Theory overpredicts all H2 broadened widths and all D2 broadened widths except those for the R(0), P(1), and P(2) lines for the Anderson treatment of close collisions. Better agreement is found with H2 broadening if the Van‐Kranendonk treatment of close collisions is used. The general conclusion reached is that the theory cannot be used reliably to predict vibration‐rotation linewidths which are dominated by forces of shorter range than dipole‐dipole.

Calculation of Radiation from Hot H 2 O and CO 2 Viewed through a Cool Intervening Atmosphere

Thermal radiation from hot water vapor and carbon dioxide imbedded in cool atmosphere, using extended molecular band models

Simultaneous Multispectral Absolute Radiometer And Transmissometer System

A mobile optical laboratory has been developed for the study of atmospheric electro-optical phenomena. This system offers significant advantages over previously fielded measurement hardware. The system incorporates 0.9 meter collecting optics; precision, motor-driven, optical support structures; secondary standard, broadband IR sources; visible and IR laser sources; a full duplex FM microwave data link; four transmissometer channels; four radiometer channels; and a high-resolution thermal imager. A modular system design combined with extraordinary mobility make this system a versatile research tool capable of addressing many diverse atmospheric electro-optical problems. A detailed description of the system is presented. The application of the system to the study of battlefield obscurant effects on electro-optical systems is demonstrated with specific examples.

Anomalous resonance effects in collision broadened spectral line widths

Abstract Calculations of self broadened DF vibration-rotation line widths and of widths of DF and HF broadened by each other have been performed using the Anderson theory. The calculations include effects of inexact resonances in the upper states of the fundamental band and also include dipole-dipole, dipole-quadropole and the quadropole-quadropole terms in the multipolar expansion. A qualitative discussion of the results is given.

Simulation of sampling effects in FPAs

The use of multiplexers and large focal plane arrays in advanced thermal imaging systems has drawn renewed attention to sampling and aliasing issues in imaging applications. As evidenced by discussions in a recent workshop, there is no clear consensus among experts whether aliasing in sensor designs can be readily tolerated, or must be avoided at all cost. Further, there is no straightforward, analytical method that can answer the question, particularly when considering image interpreters as different as humans and autonomous target recognizers (ATR). However, the means exist for investigating sampling and aliasing issues through computer simulation. The U.S. Army Tank-Automotive Command (TACOM) Thermal Image Model (TTIM) provides realistic sensor imagery that can be evaluated by both human observers and TRs. This paper briefly describes the history and current status of TTIM, explains the simulation of FPA sampling effects, presents validation results of the FPA sensor model, and demonstrates the utility of TTIM for investigating sampling effects in imagery.