P. Duggan

Departures from the soft collision model for Dicke narrowing: Raman measurements in the Q branch of D2

With high quality spectral data, we have observed departures from the soft collision model for translational motion, in the transition region from Doppler broadening to Dicke narrowing. The departures are in agreement with theoretical calculations based on the Boltzmann equation. The implications of the results concerning the dynamics of fluids are discussed. In addition we show that the mass diffusion constant describes the translational diffusion of the optical coherence and we give precise measurements of the broadening coefficients of the Q(0) to Q(6) lines.

Spectroscopic technique for measuring the temperature and pressure cycle of a pressure modulator radiometer.

Precise spectral line measurements of carbon monoxide in an operating pressure modulator cell permit independent determinations of the instantaneous gas temperature and pressure.

Lineshape analysis of speed dependent collisional width inhomogeneities in CO broadened by He, N2, and Xe

We present high resolution (10−4 cm−1) and high signal to noise ratio (2000) infrared lineshapes of CO perturbed by Xe, N2, and He in the intermediate regime from Doppler to collision broadening. It is found that the pressure broadened component of the lineshape cannot be fit by a Lorentzian lineshape. A speed dependent collisional width is required to fit the spectra, particularly when broadened by the larger Xe perturber. Based on the theory of Robert et al. [1992], a collision broadening lineshape model is derived, and we also include the effect of Dicke narrowing.

Broadening and shifting of the Raman Q branch in pure D2 and D2‐He mixtures

We report the broadening and shifting of the Raman Q branch lines in D2 and D2 ‐ He mixtures, all at 305.2 K. From a linear fit of the widths and shifts as a function of density we have determined broadening and shifting coefficients with an uncertainty of ±0.5%. None of the existing semi‐classical or quantal coefficient agree with the measurements at this level of accuracy. As well we discuss nonlinear contributions to the widths and shifts. Measurements of the broadening of the depolarized part of the Q branch in D2 are reported for the first time.

Dynamic measurement of gas temperature and pressure using infrared spectroscopy

The changing thermodynamic state of a pressure modulated gas sample near room temperature has been measured spectroscopically. Gas temperature was determined within 1 K from the ratio of the integrated absorptions of two vibrorotational lines, while the integrated absorption from one line was used to measure the pressure.