Ab initio studies of the low-lying states of BeO (original) (raw)

Spectroscopy and metastability of BeO +

Journal of Physics B: Atomic, Molecular and Optical Physics, 2008

The potential energy curve of the ground electronic state of BeO and those of the lowest electronic states of the BeO + cation are computed using the CASSCF/MRCI methods and a large basis set. For the cation, the spin-orbit coupling and the transition momentum integrals are also evaluated. These data are used later to deduce an accurate set of spectroscopic constants and to investigate the spin-orbit-induced predissociation of the lowest electronic excited states of BeO + . Our calculations show that the high-rovibrational levels of the BeO + (1 2 + ) electronic state exhibit rapid predissociation processes forming Be + ( 2 S) + O( 3 P). Our curves are also used for predicting the single ionization spectrum of BeO.

A theoretical description of the lowest lying electronic states of the BeH2+ dication

Journal of Molecular Structure: THEOCHEM, 1993

The four lowest lying electronic states of the BeH *+ dication are described theoretically using the multireference. single and double excitations configuration interaction approach. Only the ground state shows a potential energy well; this well is very shallow and supports at least eight vibrational levels. Although the ground state is thermodynamically unstable, this potential well arises as the interaction between the potential energy curves representing the structures BeH+-H+ and Be*+-H. Dipole and transition moment functions are also calculated for all states and radiative transition probabilities and lifetimes are computed for rovibrational transitions in the ground electronic state; vibrational and rotational constants are also reported for this state.

The ground-state spectroscopic constants of Be2 revisited

Chemical Physics Letters, 1999

Extensive ab initio calibration calculations combined with extrapolations towards the infinite-basis limit lead to a ground-state dissociation energy of Be 2 , D e =944±25 cm −1 , substantially higher than the accepted experimental value, and confirming recent theoretical findings. Our best computed spectroscopic observables (expt. values in parameters) are G(1)−G(0)=223.7 (223.8), G(2) − G(1)=173.8 (169±3), G(3) − G(2)=125.4 (122±3), and B 0 =0.6086 (0.609) cm −1 ; revised spectroscopic constants are proposed. Multireference calculations based on a full valence CAS(4/8) reference space suffer from an unbalanced description of angular correlation; for the utmost accuracy, the (3s, 3p) orbitals should be added to the reference space. The quality of computed coupled cluster results depends crucially on the description of connected triple excitations; the CC5SD(T) method yields unusually good results because of an error compensation.

Electronic Structures and Transition Properties of BeSe and BeTe Molecules

ACS Omega

The electronic structure of BeSe and BeTe molecules has been investigated using the ab initio CASSCF/(MRCI + Q) method at the spin-free and spin-orbit level. The potential energy curves, the permanent dipole moment, the spectroscopic constants T e , R e , ω e , and B e , and the dissociation energy D e are determined in addition to the vertical transition energy T v. The molecules' percentages of ionic character are deduced, and the trends of the spectroscopic constants of the two molecules are compared and justified. A ro-vibrational study is performed using the canonical function approach to calculate the constants E v , B v , and D v and the turning points R min and R max. All the ground-state vibrational levels have also been investigated. The radiative lifetimes of vibrational transitions among the electronic ground states are also discussed. The results for BeSe have been compared with the previously published data while those for BeTe molecules are presented here for the first time.

The Versatile Personality of Beryllium: Be(O2)1–2 vs Be(CO)1–2

The Journal of Physical Chemistry A, 2017

To reveal the diverse chemistry of beryllium we employ multi-reference methodologies to study the ground and several excited electronic states of the titled beryllium oxides and carbonyls. The two types of complexes serve as model systems to describe the various ways that beryllium can form chemical bonds. Be(O 2), its isomer OBeO, and Be(O 2) 2 are ionic compounds where beryllium is best represented in its Be(II) oxidation state. On the other hand, CO induces the excitation of one or two 2s electrons of beryllium to its 2p shell. In this manner, the beryllium core (Be 2+) is exposed and enables the formation of dative bonds from the lone pair of carbonyls to Be. For all of the considered electronic states we provide accurate optimal geometries and excitation energies.

Fourier transform emission spectroscopy of the A 2PiX2Sigma+ system of BeH

Chemical Physics, 1998

The A 2 ⌸ -X 2 ⌺ ϩ transition of BeH was observed by Fourier transform emission spectroscopy using a hollow cathode discharge lamp. The 0-0 to 6-6 bands were rotationally analyzed and molecular constants extracted. The equilibrium rotational constants B e and bond lengths were found to be 10.331 21͑50͒ cm Ϫ1 and 1.341 68͑3͒ Å for the ground state and 10.466 31͑27͒ cm Ϫ1 and 1.332 99͑2͒ Å in the excited state. In order to link the diagonal bands together and to determine the vibrational constants, the 0-1 to 6-7 bands in an archival arc emission spectrum were also rotationally analyzed. In the X 2 ⌺ ϩ and A 2 ⌸ states, the spectroscopic constants are nearly identical so the ⌬vϭϪ1 bands were too weak to be seen in our Fourier transform spectra. Franck-Condon factors were calculated for the A 2 ⌸ -X 2 ⌺ ϩ transition from Rydberg-Klein-Rees potential curves. These new rotational analyses now link up with the previous work on the 0-7, 0-8, 0-9, 1-9 and 1-10 bands of the C 2 ⌺ ϩ -X 2 ⌺ ϩ system ͓R. Colin, C. Drèze, and M. Steinhauer, Can. J. Phys. 61, 641 ͑1983͔͒. Spectroscopic data are thus available for all bound ground state vibrational levels, vЉϭ0 -10, and a set of Dunham Y constants were determined. BeH joins the small group of chemically bound molecules for which a nearly complete set of ground state rovibronic energy levels are known experimentally.

On the X2Σ+, A2Π, and C2Σ+ states of BeH, BeD, and BeT

Journal of Molecular Spectroscopy, 2006

New Fourier transform measurements for the A 2 P À X 2 R + system of BeH are combined with previously published A À X data for BeH, BeD, and BeT, with existing data for the C 2 R + À X 2 R + system, and with recent vibration-rotation data for BeH and BeD, and fitted using combined-isotopologue Dunham expansion and direct-potential-fit methods. This data set provides direct spectroscopic information spanning 95% of the ground X 2 R + state potential well, and provides the most comprehensive spectroscopic description of this state reported to date. The analysis of this data set allows us to study the breakdown of the Born-Oppenheimer approximation for a metal hydride from the minimum of the potential well to near the dissociation limit. Improved molecular constants are also determined for the A 2 P and C 2 R + states.

A study of the Be2+—H2O system by means of ab initio calculations

Chemical Physics Letters, 1986

The Be2+-Hz0 system has been taken as an example in order to investigate the changes induced in water molecules on coordination. Pronounced changes in water geometry and vibrational frequencies are found. Optimised geometries of Bez+-water complejres are presented.