Knowledge Bank

A new, liquid helium cooled collisional cooling cell has been construeted for use in spectral simplification experiments. The cell was cooled in a Janis vaporization cryostat and spectra were measured using a Bruker high resolution Fourier transform infrared spectrometer. Diagnostic tests of this cell using $C2H2,N2O$, and $CCIF3$ injected into a helium buffer gas show that the cell can be a useful tool for future simplification experiments. The initial failures and later successes of these tests revealed important information on the required operational parameters. Near-infrared measurements of $C2H2$ seemed to show only moderate cooling of the gas. However, in the overtone region, the S/N ratio was not adequate for useful diagnostics, and the spectrum was only observed for excessive injector flow rates. In the mid-infrared region, measurements of $N2O$ yielded very acceptable rotational temperatures $(T_{rot} = 76 K $ for $Tcell=50K)$. Measurements of $CCIF3$ lines were taken to demonstrate the capabilities of collisional cooling with this system for spectral simplification.