Engineering topics
Publications and source records attributed to Chackerian, C..
Recent studies involving measurements of weak C02 bands in the near-infrared were undertaken primarily to provide improved absorption parameters to model the night-side emission spectrum of Venus.
A substantial set of CO2 spectra from 4500 to 12000 /cm has been obtained at Ames with 1500 m path length using a Bomem DA8 FTS. The signal/noise was improved compared to prior spectra obtained in this laboratory by including a filter wheel limiting the band-pass of each spectrum to several hundred/cm. We have measured positions of lines in several weak bands not previously resolved in laboratory spectra. Using our positions and assignments of lines of the Q branch of the 31103-00001 vibrational band at 4591/cm, we have re-determined the rotational constants for the 31103f levels. Q-branch lines of this band were previously observed, but misassigned, in Venus spectra by Mandin. The current HITRAN values of the rotational constants for this level are incorrect due to the Q-branch misassignments. Our prior measurements of the 21122-00001 vibrational band at 7901/cm were limited to Q- and R-branch lines; with the improved signal/noise of these new spectra we have now measured lines in the weaker P branch.
The 1996 HITRAN database incorporated an extensive update of NO line parameters in the 5.3 mue region. Hyperfine lines associated with the 0-1 band up to J=46.5 were included and accuracies were greatly imporved.
Molecular rotational and vibration-rotation spectroscopy can be a powerful tool for determining abundances and physical conditions in gases over a wide range of molecular abundance, temperature and to some extent pressure. In this paper I discuss experimental requirements for obtaining absolute intensity standards for stable molecules as well as radical molecular species. I also review the application of absolute and relative molecular intensity information for determining "conditions" in equilibrium and non-equilibrium gases.
Zeeman spectra of the v3 fundamental (at approximately 1620 c/m) of nitrogen dioxide (14N02) have been recorded with magnetic fields of approximately 500 Gauss using a FTS (at the Kitt Peak National Observatory), as well as a tunable diode laser. At low magnetic fields the Zeeman effect is small compared to the spin-rotation interaction, and the Zeeman tuning rates are expected to be linear with magnetic field. Measured tuning rates of the Q-branch (KA = 2 - 9, N = 2 - 6) sigma transitions are compared to those expected for 2Sigma transitions in low magnetic fields, 2mu ogB/(2N+l). These measurements are required in the data analysis of an ultra-sensitive (pptv) in situ detector based on magnetic-rotation spectroscopy.