Theoretical Study of the Electronic Structure and Spectroscopic Properties of a New Diatomic Molecule: BeB

Abstract

This study reports reliable theoretical evidence of the existence of a new diatomic molecule, the species BeB.Complementing previous investigations predicting also the existence of new species like BeN and BeC, it allows one to have now a global view of the properties and bonding of diatomics of beryllium with first/ second row atoms. The electronic structure was studied at the multireference single and double excitations configuration interaction (MRSDCI) level as implemented in the MELD codes and with natural orbitals (for the 42-state) as the one-particle basis. Eighteen electronic states have been characterized with the ground state being a X211 with a relatively long equilibrium intemuclear distance (Re = 3.654 %) and a sinal1 dissociation energy (De = 0.86 eV). The next doublet is also weakly bound with Re = 3.982 and De = 0.48 eV. These states are followed by two close-lying quartets at 0.568 eV (a42-), Re = 3.246 ao, and at 0.593 eV (b4n), Re = 3.460 ao, with much deeper potentials, 3.04 and 3.02 eV, respectively. The curves crossings between these three excited states and another group of four doublet states lying between 1.5 and 1.8 eV will certainly be responsible for a complex structure in the spectra of this molecule. Complementing the electronic description of all states, vibrational and rotational constants are also presented as well as dipole moment functions and vibrationally averaged dipole moments. A graphical display of contour maps of the valence orbitals as a function of the intemuclear distance clearly illustrates the electron rearrangements occumng during molecule formation and the participation of beryllium 2p orbital in a n-type bond. BeB shows more resemblance with the isoelectronic molecule B2' rather than with BeC'. A comparison of the ground state spectroscopic properties of BeB with the other firsthecond row beryllium diatomics is also presented.

The low-lying electronic states of BeI: Accounting for spin–orbit effects on the energetic profile characterization and molecular properties

“…These energies were corrected by an estimate of the contribution of the missing higher excitations needed to reach the full configuration interaction limit known as the Davidson correction (+Q) [16,17]. Spectroscopic parameters were obtained by standard fitting procedures as described in previous studies [18][19][20][21]. With the program Intensity, we also evaluated the Einstein spontaneous emission coefficients, A , (in s −1 ), as given by the expression below for the case of rotationless potentials,…”

The electronic states of SeF: A reinterpretation of the chemiluminescent emission of the reaction of selenium with fluorine

“…25 We note that the interpolated energies include the Davidson estimate to the full configuration interaction limit ͑MRCI+ Q͒. 26,27 As detailed in previous works of our group, [28][29][30][31][32][33] spectroscopic constants were obtained by standard fitting procedures.…”

“…Following standard fitting procedures, 15,[28][29][30][31][32][33] these spacings have been used to determine the vibrational constants listed in Table I. As to the rotational constants B e , they were also calculated by standard fitting schemes using the vibrational state dependent rotational constant B v , a quantity which will permit a more direct comparison with experimental data when they become available; these constants, listed in Table III, were evaluated as the vibrational average ͗v͉16.8578/ R 2 ͉v͘, where ͉v͘ stands for the vibrational wave function, is the reduced mass, R is the internuclear distance, and the numerical factor makes B v directly expressed in cm −1 .…”

Electronic structure and spectra of a new molecular species: SI. A theoretical contribution

“…Solution of this equation by the Numerov method as implemented in the program INTENSITY [29] provided rovibrational energies and wavefunctions from which spectroscopic constants were obtained by standard fitting procedures as described in the literature [30][31][32]. The calculation of transition probabilities, also implemented in the INTENSITY program, and radiative lifetimes are described in previous works and will not be detailed here [33,34].…”