Formaldehyde, 18O isotopic species
Species tag 032503
Date of EntryFeb. 2017
ContributorH. S. P. Müller

This is an update of version 1 from Mar. 2000. The experimental data were summarized by
(1) H. S. P. Müller and F. Lewen, 2017, J. Mol. Spectrosc. 331, 28.
Besides new data betwen 1.37 and 1.5 THz from that study, transition frequencies were taken mostly from
(2) H. S. P. Müller, R. Gendriesch, F. Lewen, and G. Winnewisser, 2000, Z. Naturforsch. 55a, 486;
and from
(3) R. Cornet and G. Winnewisser, 1980, J. Mol. Spectrosc. 80, 438.
Additional transition frequencies with 1H hyperfine splitting were taken from
(4) K. D. Tucker, G. R. Tomasevich, and P. Thaddeus, 1971, Astrophys. J. 169, 429;
and from
(5) K. D. Tucker, G. R. Tomasevich, and P. Thaddeus, 1972, Astrophys. J. 174, 463.
Three more transitions are from
(6) J. C. Chardon, C. Genty, D. Guichon, N. Sungur, and J. G. Théobald, 1974, Rev. Phys. Appl. 9, 961;
and one more from
(7) D. Dangoisse, E. Willemot, and J. Bellet, 1978, J. Mol. Spectrosc. 71, 414.
The predictions should be accurate enough for all astronomical observations. Predictions with calculated uncertainties exceeding 0.2 MHz should be viewed with caution.
The 1H hyperfine splitting can be resolved for Q-branch transitions with low values of J and Ka = 1. Transitions with Ka = 2 do not show hyperfine splitting while those with Ka = 3 are deemed to be too high in energy. A separate hyperfine calculation is provided. The partition function takes into account the hyperfine splitting.
At low temperatures, it may be necessary to discern between ortho-H2C18O and para-H2C18O. The ortho states are described by Ka odd, the para states by Ka even. The nuclear spin-weights are 3 and 1 for ortho-H2C18O and para-H2C18O, respectively. The JKaKc = 111 is the lowest ortho state. It is 10.4890 cm–1 above ground.
The dipole moment was assumed to be the same as for the main isotopic species, see e030501.cat.

Lines Listed2027
Frequency / GHz< 5000
Max. J54
log STR0-14.0
log STR1-7.5
Isotope Corr.-2.693
Egy / cm–10.0
 µa / D2.3317
 µb / D 
 µc / D 
 A / MHz281961.4
 B / MHz36902.276
 C / MHz32513.406
detected in ISM/CSMyes

Database maintained by Holger S. P. Müller and Sven Thorwirth, programming by D. Roth and F. Schloeder