Within physics, the diatomic constants are mainly used in astrophysics/astronomy and chemical physics. In astrophysics, they are predominantly used when analysing star spectra. For example, a group of European scientists completed ’a grid of MARCS model atmospheres for S-stars’ in 2008 (1) which used data from the Huber-Herzberg database for analysis of the spectra of stellar atmospheres. In chemical physics, calculated values are generally checked against the database’s experimental values to identify any major errors and this can sometimes also indicate the level of uncertainty in the value. An example of this is the multiple studies of h³Δ₁ in thorium monoxide that have been carried out for the electron electric dipole moment search, where the calculated values of transition energy and molecule frame dipole moment were checked against the Huber-Herzberg experimental data, and it was also used to estimate an uncertainty value (2). One study used term energy values from the database in their calculations (3).
Within chemistry, the most common areas of use are thermochemistry and molecular chemistry. In thermochemistry, the constants are once again mostly used to confirm properties of molecules. For example, a group of scientists calculated atomisation energies of molecules containing 3d transition metals in 2013 and used the database’s dissociation energy values in their calculations (4). In molecular chemistry there is one particular investigation which frequently uses the Huber-Herzberg database – the investigation into the chemical bonds of C₂. These studies use values from the database for calculations, for example vibrational frequencies and quadratic force constants (5).
There are a few interdisciplinary fields of science which also make use of the Huber-Herzberg database. In nanoparticles, it has been used in investigations of the reactivity of gold clusters to check values of dissociation energy and bond length of the molecules of Au₂ and AuH and H₂ (6). In atmospheric science the database has been used for analysing atmospheric spectra. In materials science it has been used in studies relating to carbon and hydrogen doping to check bond lengths and binding energies.
Article 1: Determination of the Cu(III)–OH Bond Distance by Resonance Raman Spectroscopy Using a Normalized Version of Badger’s Rule (2017)
· http://pubs.acs.org/doi/abs/10.1021/jacs.7b00210
Andrew D. Spaeth , Nicole L. Gagnon, Debanjan Dhar , Gereon M. Yee, and William B. Tolman
· This paper aims to find the bond distance - the average distance between the two nuclei - of this particular molecule.
· The authors state that using the Huber and Herzberg database, the relationship in calculating the bond length between diatomic molecules will often vary. Therefore, they say it is difficult to generalise a calculation for finding bond lengths using their particular method.
Article 2: Origin of the nano-carbon allotropes in pulsed laser ablation in liquids Synthesis (2017)
· http://www.sciencedirect.com/science/article/pii/S0021979716305720
David Amans , Mouhamed Diouf, Julien Lam, Gilles Ledoux, Christophe Dujardin Univ Lyon
· The authors used the molecular constants to compute energy levels (such as electronic, vibrational and rotational) to produce a calculated spectra. This was compared to the experimental data using plasma spectroscopy, as well as various other experimental methods, to conclude the reason for why diamond nanoparticles form in liquids by laser – probably due to the shockwave effects.
Article 3: BaF radical: A promising candidate for laser cooling and magneto-optical trapping (2017)
· http://iopscience.iop.org/article/10.1088/1674-1056/26/3/033702/meta
Liang Xu (许亮), Bin Wei (魏斌), Yong Xia (夏勇), Lian-Zhong Deng (邓联忠) and Jian-Ping Yin (印建平)
· The paper concludes that BaF radicals are a natural contender to be used in laser cooling, where BaF can be cooled to nearly absolute zero (0K). This is due to BaF’s excited state not having a bond distance much longer than the ground (lowest energy) state of BaF when it absorbs photons from lasers. The data for bond distance was collated by the Huber and Herzberg database.
Article 4: Consistent structures and interactions by density functional theory with small atomic orbital basis sets
Stefan Grimme, Jan Gerit Brandenburg, Christoph Bannwarth, and Andreas Hansen
· http://dx.doi.org/10.1063/1.4927476
· Density Functional Theory (or DFT) is a method in which we are able to do calculations concerning electronic structures. This method however is lacking of proper theory to explain why it does work (kind of a bunch of random numbers that just seems to work experimentally). As well as this it is only applicable on particular molecules (does not work on ones which are too small or big) and can possibly be expensive. This paper is suggesting a more efficient method to calculate these electronic structures and proposes a ‘the three small basis set approaches’ instead of using TPSSD3/M and the hybrid PBE0-D3/M which are ‘computationally expensive’ however still very accurate. The Huber Herzberg Database’s values of diatomic constants are required as references, in this case the light main group bonds for its calculations to explore equilibrium bond distances of small molecules, such as ‘first and second row molecules, heavy main group covalent bonds, and 3d-transition metal complexes.’ (10)
It is evident that the Huber-Herzberg database has been used many times across all disciplines of science since its creation in 1976 and therefore should be considered essential for the advancement of science. In particular, we should strive to maintain the database’s accuracy as it is used so frequently and has a great impact on the outcomes of many different studies.
References
(1) B. Gustafsson, B. Edvardsson, K. Eriksson, U. G. Jørgensen, A. Nordlund, and B. Plez, “A grid of marcs model atmospheres for late-type stars-i. methods and general properties,” Astronomy & Astrophysics, vol. 486, no. 3, pp. 951–970, 2008.
(2) L. Skripnikov and A. Titov, “Theoretical study of thorium monoxide for the electron electric dipole moment search: electronic properties of h³Δ₁ in ThO,” The Journal of chemical physics, vol. 142, no. 2, p. 024301, 2015.
(3) A. Petrov, L. Skripnikov, A. Titov, N. Hutzler, P. Hess, B. O’Leary, B. Spaun, D. DeMille, G. Gabrielse, and J. Doyle, “Zeeman interaction in ThO h³Δ₁ for the electron electric-dipole-moment search,” Physical Review A, vol. 89, no. 6, p. 062505, 2014.
(4) D. H. Bross, J. G. Hill, H.-J. Werner, and K. A. Peterson, “Explicitly correlated composite thermochemistry of transition metal species,” The Journal of chemical physics, vol. 139, no. 9, p. 094302, 2013.
(5) G. Frenking and M. Hermann, “Critical comments on “one molecule, two atoms, three views, four bonds?”,”Angewandte Chemie, vol. 125, no. 23, pp. 6036–6039, 2013.
(6) M. Gao, A. Lyalin, M. Takagi, S. Maeda, and T. Taketsugu, “Reactivity of gold clusters in the regime of structural fluxionality,” The Journal of Physical Chemistry C, vol. 119, no. 20, pp. 11120–11130, 2015.
(10) [116] K. P. Huber and G. Herzberg, in Constants of Diatomic Molecules, Molecular Spectra and Molecular Structure Vol. 4 (Van Nostrand, Princeton, 1979).