W. S. Benedict

ROTATION-VIBRATION SPECTRA OF DEUTERATED WATER VAPOR

Spectra of heavy water have been obtained under high resolution between 1.25—4.1μ (2400—8000 cm—1). Approximately 4500 lines have been measured, and the majority of them analyzed into ten bands of D2O and nine bands of HDO. The analysis is described in some detail, spectra of all bands are shown and a partial table of lines and a complete table of energy levels are presented. The vibration‐rotation constants are derived and compared with those of H2O.

Calculation of Line Widths in H2O‐N2 Collisions

Anderson’s general theory of collision line broadening has been applied to H2O‐N2 encounters. The only attractive force was assumed to be that between the H2O dipole, μ = 1.87×10−18 esu, and the N2 quadrupole, qN2, an adjustable parameter. A second adjustable parameter, bm, the distance of closest approach, includes the effects of all other forces. The IBM 704 was used in the calculation. Effects of varying the parameters were noted for a number of lines, and in the final calculation, which yielded the widths of all significant type B transitions up to J″ = 13, parameters qN2 = 2.62×10−26 esu and bm = 3.2 A which give an exact fit of the observed width of the microwave line 6−5−5−1, were adopted. The temperature dependence of the line width over the range 220–2400 °K, and the effects of vibration‐rotation interactions were also calculated. At 300 °K widths vary from 0.11115 cm−1 atmos for 11−1−1 to 0.03200 cm−1 atmos−1 for 14−13−13−13, there being a general decrease in width with increasing J, and at a gi...

Calculation of line widths in H2O-H2O and H2O-O2 collisions

Abstract Andersons general theory of collision line broadening has been applied to the calculation of the widths of a large number of pure-rotational transitions in H2O, self-broadened by H2O and foreign gas broadened by O2. In the former case only dipole-dipole forces were considired, in the latter only dipole-quadrupole. The method of calculation followed that previously reported for H2O-N2, and was performed on the IBM 7090. The self-broadened widths, at 300° and 360°K, are presented in tabular form; some regularities and averages are graphed and discussed. There is a marked variation from line to line, both in the absolute value and the ratio of self-broadening to N2-broadening. The intensity-weighted value of the latter ratio is 5·49, in agreement with experiment. Individual widths show fair correlation with the few available experimental values. The H2O-O2 widths depend on the uncertain value of the oxygen quadrupole, and are presented only graphically. The correlation with H2O-N2 is close enough so that the H2O-N2 results may be used for atmospheric problems.

Infrared Line and Band Strengths and Dipole Moment Function in HCl and DCl

Strengths of the individual isotopic lines have been measured in the 2–0, 3–0, 2–1, and 3–2 bands of HCl35 and HCl37 and in the 1–0, 2–0, and 3–0 bands of DCl35 and DCl37. The relative line strengths for the 1–0 band of DCl are shown to agree with that expected theoretically including the effect of the interaction of vibration and rotation, but the line strengths in the 2–0 bands agree about equally well with the rigid rotor and with the theoretical expressions including the vibration‐rotation interaction. Experimental band strengths and vibrational matrix elements are derived from the measured line strengths for each band. These data are combined with previous results on the HCl 1–0 band to obtain power series expansions for the electric dipole moment function of the hydrogen chloride molecule. It is found that the effective charge is of the same sign as the permanent moment and that the second derivative of the dipole moment with respect to internuclear distance at re is probably of opposite sign. In general, for the same number of terms in the dipole moment expansion it is found that Morse vibrational wave functions give considerably better agreement between observed and calculated matrix elements than do anharmonic oscillator functions retaining terms in the potential energy through the fourth power in the internuclear separation.

Infrared Spectra of H2O and CO2 at 500°C

A porcelain‐lined absorption cell of the Pfund type is described, in which 3 meters of gas may be heated to temperatures above 500°C. The spectra of air at atmospheric pressure containing varying amounts of H2O and CO2 have been obtained in this cell between 2.4–15μ with a prism spectrometer, and between 13–25μ with a grating spectrometer giving spectral resolution of about 2 cm−1. A number of new lines in the pure rotation spectrum and the ν2vibration of H2O, originating from levels of high energy, have been observed and classified. New CO2 bands in the regions of 11–20μ and 5μ have also been observed, originating from levels as high as 5ν2, and leading to improved values of higher‐quanta levels of ν2 and vibrational constants for this molecule.

Vibration-Rotation Bands of Ammonia. IV. The Stretching Fundamentals and Associated Bands near 3 μ

High‐resolution spectra of NH3, yielding 1800 lines between 3060–3580 cm−1, are presented. Analysis of the ν3 fundamental is complete through J′=9 and presents no unexpected features. Resolution of the K substructure in the ν1 fundamental shows that several perturbations are present. The most important of these, involving a Fermi resonance with the parallel component of 2ν4, and a Coriolis resonance with its perpendicular component, are clarified. Lines in both components of 2ν4 are identified through J′=6, and a strong Coriolis interaction between the l=0 and l=2 states is observed and discussed.

Vibration-Rotation Bands of N 2 O†*

The spectrum of nitrous oxide has been measured with a high-resolution grating spectrometer in the region from 2395 to 3510 cm−1. Long absorbing paths were used in a heated cell, so that it was possible to observe many of the weaker bands, including those with lower vibrational levels ν2, 2ν20, 2ν22, and ν1. Accurate values of the rotational constants have been obtained, including the l-type doubling and variations with v and l of the centrifugal stretching constant. These have been correlated with other data to obtain improved values of the molecular constants, with particular attention to the Fermi interaction. Other weak interactions are observed and discussed.

Absorption Bands of Carbon Dioxide from 2.8–4.2 μ

The high-resolution spectrum of CO2 has been studied between 2.8 and 4.2 μ, by using up to 48 meter-atmospheres path to develop weak bands. Accurate band constants have been obtained for the transitions 1310–000, 0510–000, and 101–0200, and fragments of new weak bands have been detected near 3500 cm−1. Estimates of band intensities are given, including a discussion of the highly abnormal intensity distribution in the weak perpendicular bands.

Vibration‐Rotation Bands of Ammonia. III. The Region 3.2–4.3 Microns

The weak absorption of NH3 between 2373–3080 cm—1 has been studied under high resolution, and a complete analysis given for over 1000 lines, including studies of the intensity and line width. The strongest bands (Sv0=0.44 and 0.20 cm—2 atmos—1, respectively) are 3ν28−0a and 3ν2a−08;ν3−ν2 (Sv0=0.074);ν3+ν2−2ν2 (Sv0=0.011);and ν2+ν4 (Sv0=0.06) have also been located. v2+v4 shows anomalous intensity behavior as well as large vibration‐rotation‐inversion‐ζ‐splitting interactions. The lines in 3v2 are 40–50% narrower than those in the microwave region, and appear symmetrical with no pressure shifts.