3. Evaluation of the Spectral Data
The evaluation has a two-fold purpose, first, the selection of the best
set of measured transition frequencies and, second, selection or calculation of
consistent and reliable spectroscopic constants. Since measured or calculated
uncertainties are the best indicators of the quality of the data, a substantial
portion of the critical evaluation effort has gone into determining these
uncertainties.
a. General Procedure
Generally, the selection of the most reliable transition frequencies posed few
problems since there were relatively few cases where duplicate measurements
have been reported for the same transition. In cases where this did occur, the
selection was based on both the overall consistency of the measurement in
question with the other spectral data available, and on the reported
uncertainty in the measurements. In nearly all cases the measurements with the
smallest uncertainties reported by the authors were found to be the most
reliable.
The determination of the most reliable molecular constants posed more severe
difficulties. Occasionally inconsistencies arose in cases where data were
reported by several independent workers who studied quite different regions of
the spectrum, e.g., molecular beam measurements vs. microwave measurements or
centimeter vs. millimeter-wave measurements. If all of the available data had
not been analyzed simultaneously in these instances, a complete reanalysis was
carried out to eliminate the discrepancies. These calculations also resulted in
the detection of a number of misprints in the literature which were not obvious
through simple inspection of the reported assignments and transition
frequencies. Since a question might arise concerning the correct value when a
difference is noted between the present compilation and the reference cited,
the following section summarizes the typographical errors, changes in notation
and other errors rectified in the present work.
b. Discussion of Specific Corrections and Reanalysis of the Data
The discussion of corrections and reanalysis for each specific molecule has been
placed at the bottom of the main page for that molecule. For some molecular species,
no corrections or reanalysis were necessary and the data reported should be
identical to that given in the original work. Note that for all linear molecules
the lower frequency stretching vibration is labeled
ν3.
