J. A. A. Ketelaar

The absorption intensity of simultaneous vibrational transitions in gas mixtures

Synopsis A formula is derived for the intensity of those simultaneous transitions in gas mixtures in which take part an infrared-active vibrational transition of one molecule and a Raman-active vibrational transition of another molecule. We applied this formula to the simultaneous transition observed in mixtures of carbon dioxide and hydrogen at 6510 cm−1. Using two different values reported in literature for the derivative of the polarizability of hydrogen with respect to the intermolecular distance, we find for the integrated binary absorption coefficient values of 0.63 × 10-3 Am−2cm−2 and 1.2 × 10−3 Am−2cm−2. The experimental value is 0.88 × 10−3 Am−2cm−2.

Simultaneous vibrational transitions

Synopsis A quantum mechanical treatment is given of two interacting harmonic oscillators with the result that simultaneous transitions are shown to be possible. The intensity ratio of difference and sum transitions is derived: I _ / I + = v A - v B v A + v B exp ( - h v B / k T ) in good accordance with experiment. Cubic terms in the potential energy are shown to have no appreciable influence. Selection rules are given. The influence of temperature derived is compared with experimental results. In the infrared absorption spectra of some mixtures bands are found at frequencies, which are the sum or the difference of a vibration frequency of one compound and a vibrational frequency of the other compound in the mixture. Two colliding molecules absorb together one quantum and undergo simultaneously a vibrational transition 1–7 ). We will give here a theoretical treatment of these simultaneous transitions, based on the quantum mechanical treatment of the harmonic oscillator.

The effective field and the frequency of overtones and combination bands in the vibration spectra of crystals

Abstract It is shown that the effective field may cause a shift of the fundamental absorption bands in a crystal, while the frequency of overtones and combination bands remains unchanged. This effect, which complicates the interpretation of overtones and combination bands, is illustrated by the absorption spectra of sodium nitrate and calcite.

Infrared emission spectrum of calcite

Abstract The polarized infrared emission and reflection spectra of calcite were measured at 300°C; the results are in quantitative agreement with Kirchhoffs law.

Far infrared emission spectrum of flames. rotational spectrum of OH-radicals and determination of flame temperatures

Synopsis The infrared emission spectra of flames of H2−O2, C2H2−O2 mixtures and of hydrogen burning in air were studied in the KBr-region. The variation of intensities of a few bands with oxygen/burning gas ratio led to distinguish these bands as belonging to the OH-rotational spectrum. Flame temperatures calculated from this spectrum are consistent with the values obtained from ultraviolet bandspectra.