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.
3.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 and most laboratories quote reliable
uncertainties. In cases where problems 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 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,
there are comments following the molecular constant tables in these cases.
