Example Perchloryl Fluoride, FClO₃

with hyperfine structure resolved to different degrees

Data of the ground vibrational level of ¹⁹F³⁵Cl¹⁶O₃ were used in the fit. The J = 0 and 1 lines were presented in the article mentioned above. Both ¹⁹F (I = 1/2) and ³⁵Cl (I = 3/2) hyperfine splitting was resolved. These lines have the state number 0.
For the observed J = 2 to 6 transitions only ³⁵Cl hyperfine splitting was resolved. These lines have the state number 1.
For the observed J = 33 to 37 transitions only no hyperfine splitting was resolved. These lines have the state number 2.

Consideration for the parameter file in the option lines 3 to 5:
The second parameter indicates the spin-multiplicities. Parameters 7 to 9 and the last one govern the spin-statistics.
The values of 1, 4, and 8 for WTPL and WTMN in fclo3.par were choosen in order to be able to use the same partition function for all "states". However, it appears as if common factors do matter in a certain way. Therefore, both WTPL and WTMN were changed to one in nohfs.var ! The value for the partition function at 300 K has been divided by 8 accordingly.

All lines have to have the same number of quantum numbers even though some are redundant for lines where no or no ¹⁹F hyperfine splitting was resolved. These are J, K, state, F₁, and F for the upper and the lower state. The parity was omitted because K-splitting was not resolved. Because of this, the mrg file contains no parity designation while it is included in the cat file.

• The fit directory has the line, parameter, fit, and variance files.
• The hfs.1K directory has all the other files related to a prediction of transitions with ¹⁹F and ³⁵Cl hyperfine splitting at a rotational temperature of 1 K. Note that the low J transitions are rather strong even though the dipole moment is with 0.0270 D not particularly large.
• The nohfs.300K directory has all the other files related to a prediction of transitions without hyperfine splitting at a rotational temperature of 300 K. Note that all transitions are fairly weak.

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Figure 1 shows a simulation of the FClO₃ pure rotational spectrum at 1 K. (Do not worry about the temperature at the top of the figure !) Note: the K structure is basically undiscernible. And only J" = 4, maybe 5 have substantial intensity.





Figure 2 shows a simulation of the FClO₃ pure rotational spectrum at 300 K. Note the different intensity and frequency scales in Figs. 1 and 2 ! At room temperature, the J" = 94, K" = 0 line is about 2.5 orders of magnitude stronger than the J" = 0 line.





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