P. M. Sinclair

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.

Anomalous broadening and shifting in D2 and D2–He mixtures

Abstract Precise and accurate measurements of the Q branch lines of D2 in D2 and D2–He mixtures at several temperatures reveal an anomalous dependence of the widths and shifts on density. At high densities the widths and shifts are linear in density but with a constant off-set when extrapolated back to zero density. At low densities the shifts exhibit normal behaviour, being proportional to the density. Low density is identified with the free streaming or Voigt region. High density is identified as the usual collision dominated regime where the Dicke width is much smaller than the collisional width. It does not appear as if any existing models or theories of isolated lines can explain the present results.

Digital divider circuit for a laser-beam-pointing stabilization system

Adigital divider circuit is used in a feedback circuit that is designed to stabilize laser-beam pointing.

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.