Speaker
Description
Theoretical energy separation (ionization, dissociation, transition energy) is composed of several
additive components. The total energy and its components for a light molecule can be well
described in the framework of the nonrelativistic quantum electrodynamic theory (NRQED) [1]
by the expansion in powers of the fine structure constant. The higher accuracy is expected,
the more components must be involved. Furthermore, the higher accuracy is expected,
the more accurate the involved components must be. In particular, the leading term
of the expansion, which represents the nonrelativistic energy, is by far the dominating one
and its accuracy can directly limit the accuracy of the total energy $E(\alpha)$. For example, attaining
the 1 MHz ($\sim 3\cdot 10^{-5}$ cm$^{-1}$) accuracy for the dissociation energy of D$_2$ requires 10 significant
figures of the nonrelativistic component to be known. A common procedure of decomposing
the nonrelativistic energy into the clamped nuclei, adiabatic, and nonadiabatic components
can hardly enable such an accuracy. For the four-body systems like deuterium molecule though,
the nonrelativistic energy can also be calculated directly, that is without expansion in a mass
parameter. Such calculations have been performed using nonadiabatic explicitly correlated Gaussian
functions reaching the accuracy of $10^{-3}-10^{-5}$ cm$^{-1}$ [2,3]. On this poster, we present results of an approach employing nonadiabatic James-Coolidge basis functions. This method enables the accuracy of $10^{-7}-10^{-8}$ cm$^{-1}$ to be obtained for the nonrelativistic dissociation energy
of an energy level and, in contrast to the aforementioned calculations, is not limited to
the rotationless states. The new nonrelativistic results, augmented by relativistic and QED
corrections, enable the accuracy which surpasses the best spectroscopic data [4-7].
References
[1] W. E. Caswell, G. P. Lepage, Phys. Lett. B 167, 437 (1986).
[2] S. Bubin, M. Stanke, and L. Adamowicz, J. Chem. Phys. 135, 074110 (2011).
[3] M. Puchalski, A. Spyszkiewicz, J. Komasa, K. Pachucki, Phys. Rev. Lett. 121, 073001 (2018).
[4] J. Liu, D. Sprecher, C. Jungen, W. Ubachs and F. Merkt, J. Chem. Phys. 132, 154301 (2010).
[5] M. Niu, E. Salumbides, G. Dickenson, K.Eikema, W. Ubachs, J. Mol. Spectrosc. 300, 44 (2014).
[6] D. Mondelain, S. Kassi, T. Sala, D. Romanini, D. Gatti, and A. Campargue, J. Mol. Spectrosc. 326, 5 (2016).
[7] P. Wcisło, et al., J. Quant. Spectrosc. Radiat. Transfer 213, 41 (2018).
