Infrared Absorption Lines Research Articles

The Double Minimum Problem Applied to Potassium Hydrogen Fluoride

The doublet character of the infra-red absorption line at 2.67μ of solid potassium hydrogen fluoride is due to the ``tunnel effect.'' The proton has two potential minima between the fluorine nuclei in the FHF− ion. The distance of a minimum to the center of the ion is 0.26A. The height of the potential hill is 33,400 calories.

Note on Brunt's Formula for Nocturnal Radiation of the Atmosphere

view Abstract Citations (3) References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Note on Brunt's Formula for Nocturnal Radiation of the Atmosphere Pekeris, C. L. Abstract It is shown that the linear dependence of the downgoing radiation of the atmosphere on the square root of the surface vapor pressure, discovered empirically by Brunt, can be explained by Dennison's theory of the shape of infra-red absorption lines. The theory is substa~ntiated by Fowle's measurements of the total absorption in the bands o.S ~, p, and ~ of water vapor Publication: The Astrophysical Journal Pub Date: May 1934 DOI: 10.1086/143552 Bibcode: 1934ApJ....79..441P full text sources ADS |

The Shape and Intensities of Infra-Red Absorption Lines

An expression for the shape of an infra-red absorption line is developed on the basis that the principal factor in the broadening of a line is the limitation of the length of wave train a molecule may absorb due to its perturbation by thermal collisions. The shape of the line is accordingly found by expanding the finite wave train with a Fourier integral and then integrating over the distribution of lengths of wave train given by the kinetic theory of gases. The absorption coefficient as found in this way may be expressed to a high approximation by means of two damping curves involving the number of molecules per unit volume, the temperature, and $\ensuremath{\sigma}$ the effective diameter.To apply this result to the analysis of observed infra-red spectra allowance must be made for the low spectrometer resolution due largely to the wide slits employed. Two expressions are developed, holding for all but very weak lines, which relate the area under the absorption line $\mathrm{Abs}$, the minimum value of the transmission ${T}_{min}$ and the true intensity $\ensuremath{\alpha}$ with the slit width $a$, the cell length $l$, and the molecular constants. $\mathrm{Abs}=\frac{{[5.412\ensuremath{\alpha}n{\ensuremath{\sigma}}^{2}\mathrm{l}]}^{\frac{1}{2}}}{{[\ensuremath{\pi}hm]}^{\frac{1}{4}}}$ $\mathrm{Abs}=\ensuremath{-}2.42a {log}_{10} {T}_{min}$It is shown that these formulae are capable of interpreting the absorption lines of the infra-red spectrum of HCl observed by R. F. Paton and yield a value of 10.8\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}8}$ cm for $\ensuremath{\sigma}$. The meaning of $\ensuremath{\sigma}$, the distance to which two molecules may approach without altering each others phases, as well as the range of validity of the assumptions is discussed and a correction to the absorption area formula for faint lines is deduced. In connection with a consideration of the absorption measurements of HCl by Kemble and Bourgin, a computation is made of the effective moving charge of the molecule giving the value $\ensuremath{\epsilon}=(.199) 4.77\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}10}$ E.S.U.