A new, low temperature long-pass cell for mid-infrared to terahertz spectroscopy and synchrotron radiation use.

A new cell has been designed for accurate spectroscopic measurements in the 80-400 K temperature range with variable path lengths from 3 to more than 141 m. The spectral coverage at these temperatures ranges from the visible to less than 10 cm(-1), thanks to the use of diamond windows. The design of the cryostat and vacuum setups allows vibration-free operation.

Upper limits for undetected trace species in the stratosphere of Titan.

In this paper we describe the first quantitative search for several molecules in Titan's stratosphere in Cassini CIRS infrared spectra. These are: ammonia (NH3), methanol (CH3OH), formaldehyde (H2CO), and acetonitrile (CH3CN), all of which are predicted by photochemical models but only the last of which has been observed, and not in the infrared. We find non-detections in all cases, but derive upper limits on the abundances from low-noise observations at 25 degrees S and 75 degrees N.