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Supplementary data for this article consists of six files.
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1. EPS file for Figure 1.

2. EPS file for Figure 2

3. EPS file for Figure 3

4. An ASCII listing of the parameters determined in the Dunham-type combined
   isotopologue fits of Table 2, and of the band constants generated from them.

In addition, if/when the paper is accepted we will provide two additional
supplemental files containing the raw data used in the analysis.  However, they
are fairly large, and it does not seem useful to burden the referee(s) disk
storage with this archival material.

5. An ASCII file listing of the data used in the combined isotopologue
   parameter-fit and potential-fit treatments of the X state.

6. A PDF file listing the data used in the A- and C-state analyses.

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