Improved Partition Functions and Related Thermochemical Quantities for the
16
O
2
and H
16
2
O
Molecules
Tibor Furtenbacher,
1
Allan H. Harvey,
2
and Attila G. Cs´asz´ar
1, a)
1)
Institute of Chemistry, ELTE E¨otv¨os Lor´and University, H-1117 Budapest,
P´azm´any P´eter s´et´any 1/A, Hungary
2)
Applied Chemicals and Materials Division, National Institute of Standards and Technology,
Boulder, Colorado 80305, USA
(Dated: May 16, 2025)
Based on the direct summation technique, improved ideal-gas partition functions and related
thermochemical quantities are reported for the parent isotopologues of molecular oxygen and
water,
16
O
2
and H
16
2
O, respectively. The new results update those of two previous publications
reported in this journal [J. Phys. Chem. Ref. Data 45, 043104 (2016) and 48, 023101 (2019)].
The improved thermochemical functions, tabulated at 1 K intervals between 0 and 5000 K in
the Supplementary Material to this paper, use (a) the exact values of the fundamental physi-
cal constants fixed in the 2019 redefinition of the SI, (b) an improved set of empirical energy
levels for H
16
2
O, with much improved uncertainties at low rovibrational excitations, (c) differ-
ent approaches to the uncertainty budget, including correcting an error in previous uncertainty
calculations for
16
O
2
, and (d) a small correction to the ideal-gas thermochemical functions of
16
O
2
, making them applicable for oxygen of natural isotopic composition, which is needed for
the development of practical thermodynamic models.
a)
Electronic mail: attila.csaszar@ttk.elte.hu
1
This is the author’s peer reviewed, accepted manuscript. However, the online version of record will be different from this
version once it has been copyedited and
typeset.
PLEASE CITE THIS ARTICLE AS DOI:
10.1063/5.0273661
