Robert E. Meredith

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.

Strengths and widths in the first overtone band of hydrogen fluoride

Abstract The strengths and self-broadened half widths of 18 lines of the first overtone band of hydrogen fluoride have been measured using a direct measurement method. The lines were assumed to have the Lorentz or combination Lorentz-Doppler shape. Matrix elements have been calculated for a dipole moment function of the form μ(r) = ΣkMk(r-re)k. Best values of M1 and M2 were found to be M1 = 1.51 x 10-10 esu and M2 = -3.74 x 10-3 esu/cm for a rotating Morse oscillator and M1 = 1.52 x 10-10 esu and M2 = -2.15 x 10-3 esu/cm for the rotating anharmonic oscillator. Line widths were calculated using the Anderson theory. The first-order effect of the vibrational quantum number on the half widths has been taken into account, and a comparison with measurements on the pure rotation and fundamental bands has been made. The measurements show good agreement with theory in that the half widths tend to decrease with increasing Δv. Also in agreement with theory, measured values in the P branch are greater than in the R branch for moderate values of |m|. As |m| increases and the shorter range forces become more important, the R-branch widths tend to become greater than the corresponding lines in the P branch.

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.

A new method for the direct measurement of spectral line strengths and widths

The most important sources of error incurred in the measurements of spectral-line parameters arise from uncertainty in the determination of the 100 per cent transmittance and in the distortion of the line profile by the spectrometer. These errors have been investigated numerically by passing an idealized spectrometer slit function over several assumed line profiles. In this way, families of correction curves have been constructed, from which spectral-line strengths, widths, and peak absorption coefficients may be determined from apparent values measured directly from the chart recorder. The effect of the form of the slit function has been investigated by using triangular, Gauss, Cauchy and combination Gauss-Cauchy slit functions. The effect of uncertainties in the line shape has been investigated by using Doppler, Lorentz, and Voigt line shapes. The correction procedure has been applied to the self- and nitrogen-broadened R(0) and P(l) lines in the first overtone band of hydrogen fluoride. The measurements were performed on collision-broadened lines near the linear region of growth ; within experimental error, the line parameters were found to obey the Lorentz relation kP = S/yn. The measured self-broadened line widths indicate a non-Lorentz behavior because they do not vary linearly with pressure. When broadened by nitrogen, the line widths follow the expected linear dependence on pressure, well within experimental error.

Infrared Absorption Spectrum of CD4 at 4500 cm—1

A high‐resolution infrared absorption spectrum is presented for the region of the first overtone of the triply degenerate vibrational fundamental ν3 of CD4. The measured lines between 4430 and 4550 cm—1 are reproduced and tabulated. Comparisons are made between the tetrahedral splittings in this spectrum and those in the spectra ν3 and ν1+ν4 of CH4.

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.

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.

Revised water vapor line parameters in the 1.0- to 1.1-μm region

Advancements in short wavelength lasers has renewed the interest in molecular extinction in the 1.0 to 2.0 micrometer region. In recent programs sponsored by three agencies: Lincoln Laboratory, the U.S. Army Strategic Defense Command, and the Atmospheric Sciences Laboratory, OptiMetrics has refined molecular parameters in this spectral region for use with both ground level and slant atmospheric paths.

Absorption and Emission Spectrum of CaF2:U3+ from 2.1 to 2.5 Microns

The emission and absorption of CaF2:U3+ has been scanned at 77° and 4.2°K and linewidths have been measured. The spectrum is interpreted as arising from ions perturbed by a weak tetragonal crystal field. Preliminary results of the Zeeman effect on the narrowest lines are presented.