Theoretical study of the alkali hydride anions XH–(X = Li, Na, and K)
Graphical abstract
For the alkali hydride molecular anions XH– (X=Li, Na, K and Rb), the potential energy curves in the representation 2s+1Λ(+/-) have been calculated along with the spectroscopic constants, the static and transition dipole moment, the Franck-Condon factor and the rovibrational calculations of the investigated electronic states.
Section snippets
Introduction:
In the late 20th and early 21st centuries, there has been a remarkable development in physics fulfilled by the progress in the methods of producing and trapping of ultracold atoms in gaseous phase [1]. Thus, several techniques were implemented in order to manipulate and study ultracold matter via the optical and electromagnetic fields leading to developed frameworks for quantum information processes [2]. Regarding the cooling of molecular species, a new range of techniques has been developed
Pure bound state computational Approach:
By the employment of the state averaged Complete Active Space Self Consistent Field (CASSCF) followed by Multireference single and double configuration interaction (MRCI) method with Davidson correction (+Q) [36] the electronic states of the alkali hydride molecular anions LiH–, NaH–, and KH– have been investigated in their doublet and quartet multiplicities. The calculation has been done by using the high-level ab initio calculations applied in MOLPRO program package [37] taking the advantage
R-Matrix method computational approach:
R-matrix method is employed in the calculation. The space is separated into an inner region which contains the molecule and its orbitals, and an outer region. In the inner region, the scattered electron is indistinguishable from the molecular electrons, and can occupy molecular orbitals [44].For molecules containing alkali metals, virtual orbitals are very diffuse. Care has to be taken to avoid linear dependencies between the continuum wave function and the virtual orbitals. A large R-matrix
Dipole bound States, stability and metastability
The adiabatic potential energy curves (PECs) that have been investigated using the pure bound state approach for the low lying electronic states of doublet and quartet multiplicities for the alkali hydride molecular anions XH– (X = Li, Na, and K) and plotted as function of the internuclear separation respectively in Fig. 1, Fig. 2, Fig. 3 and Figs. (FS1-FS3) in the supplementary material. The origin is taken at 8.03 Hartree, 162.46 Hartree, and 599.75 Hartree for LiH–, NaH–, and KH–
Conclusion:
For the alkali hydride molecular ions LiH–, NaH–, and KH–, the potential energy curves have been investigated via spin free study by implementing MCSCF/MRCI and R-matrix technique. Comparison between R-matrix and pure bound state results have shown that the results related to the MCSCF/MRCI excited states of LiH- may be representative of NMFE states. Most of the doublet states of NaH -and KH- ions have deep potential wells while those of quartet states are entirely shallow. The spectroscopic
CRediT authorship contribution statement
Israa Zeid: Software, writting. Nayla El-Kork: Funding acquisition, Writing - review & editing. Sally Al Shawa: Data curation, Formal analysis. Mahmoud Korek: Supervision.
Acknowledgements
This publication is based upon work supported by the Khalifa University of Science and Technology under Award No. CIRA-2019-054. The authors would like to acknowledge the use of MASDAR High power computer, Khalifa University Nuclear Engineering Department High power computer and Ankabut High Power computer for the completion of their work. Also, the authors would like to acknowledge Quantemol team for pursuing the R-Matrix method calculations.
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