High-resolution tunable mid-infrared spectrometer based on difference-frequency generation in AgGaS2.

We have built a high-resolution and high-signal-to-noise ratio spectrometer for line shape studies of greenhouse gases in the mid infrared. The infrared radiation is generated in a AgGaS2 nonlinear crystal by the well-known difference-frequency method. The choice of crystal is explained, and a brief literature review is presented.

Broadening and line mixing in the 20 (0)0<--01 (1)0, 11 (1)0<--00 (0)0 and 12 (2)0<--01 (1)0 Q branches of carbon dioxide: experimental results and energy-corrected sudden modeling.

Using both a difference frequency spectrometer and a Fourier transform spectrometer, we have measured transitions in the 12 (2)0<--01 (1)0 band of carbon dioxide at room temperature and pressures up to 19 atm. The low-pressure spectra were analyzed using a variety of standard spectral profiles, all with an asymmetric component to account for weak line mixing. For this band, we have been able to retrieve experimental line strengths and the broadening and weak mixing parameters.

Dynamic spectroscopic measurements of the temperature and pressure cycles in a MOPITT pressure modulator cell.

The temperature and pressure cycles inside a pressure modulator cell (PMC) of the type used for gas-correlation radiometry aboard the Measurements of Pollution in the Troposphere (MOPITT) satellite instrument have been determined from dynamic measurements of the spectral line shapes of the R(0) and R(18) transitions in the fundamental vibrational-rotational band of carbon monoxide. The line strengths and linewidths were used to calculate the temperature and pressure, respectively, with a temporal resolution of approximately 200 micros, or 1/100 of a PMC cycle. The results are compared with a thermodynamic box model.