States Of BO Research Articles

Theoretical study of laser cooling of the BO+ molecular ion

The feasibility of laser-cooling BO+ cation is investigated by using the high-level ab initio calculation method. The potential energy curves (PECs) of the 24 Λ-S states are studied by the multi-reference configuration interaction (MRCI) method. The calculated spectroscopic constants of bound states of BO+ are in good agreement with available experimental and theoretical results. The dipole moments (DMs) of the BO+ ion are obtained and the transition dipole moments (TDMs) of 21Σ+-X1Σ+, 31Σ+-X1Σ+, 11Π-X1Σ+, 21Π-X1Σ+, 31Π-X1Σ+ and 21Π-11Π are calculated. Based on the computed PECs, the Franck-Condon factors (FCFs) of the 21Σ+-X1Σ+ transition are found to be highly diagonal. The radiative lifetime of the 21Σ+-X1Σ+ transition is calculated to be 36.73 ns, which is sufficiently short for laser cooling. The Einstein coefficient A and branching ratio R are evaluated, and the possibility of laser-cooling BO+ cation is discussed.

Investigations on transition properties of X2Σ+, A2Π, B2Σ+, C2Π, and a4Σ+ states, and their Ω states of BO

The transition properties were calculated for the X2Σ+, A2Π, B2Σ+, C2Π, and a4Σ+ states, and eight Ω states of BO. The calculations were performed using the CASSCF method, followed by the icMRCI approach. Core–valence correlation and relativistic corrections were included. The radiative lifetimes of the first 16 vibrational levels were roughly 1.5–1.6 μs for the A2Π state, 96–177 ns for the B2Σ+ state, and 16.7–18.5 ns for the C2Π state. The B2Σ+ – X2Σ+ and C2Π – X2Σ+ transitions were strong, followed by the A2Π – X2Σ+, B2Σ+ – A2Π, and C2Π – A2Π transitions. The radiative lifetime of the first 16 levels was approximately 4.9–10.4 ms for the a4Σ+1/2 state, 0.21–24 ms for the a4Σ+3/2 state, 2.9–3.6 μs for the A2Π1/2 state, 3.5–3.8 μs for the A2Π3/2 state, 134–230 ns for the B2Σ+1/2 state, 23.2–25.4 ns for the C2Π1/2 state, and 23.0–25.2 ns for the C2Π3/2 state. Among all spin–forbidden transitions generated from the a4Σ+ state, the a4Σ+1/2 – X2Σ+1/2 and a4Σ+3/2 – X2Σ+1/2 transitions were relatively strong. The transition properties reported herein were compared with the experimental results. The variation of the radiative–lifetime distribution with the rotational angular quantum number was evaluated for A2Π1/2, A2Π3/2, B2Σ+1/2, C2Π1/2, and C2Π3/2 states. It is expected that the transition properties calculated in this study can provide some useful guidelines for future experimental and theoretical investigations.

A theoretical study of the BO 2+ dication

Potential energy curves for twelve low-lying electronic states of the BO 2+ dication have been calculated using internally contracted multireference MRCI, MRCI+Q and ACPF methods and the coupled-cluster RCCSD(T) approach. Spectroscopic constants and transition energies of BO 2+ have been determined and the double ionization energy of BO has been estimated. The spin-orbit induced predissociation from the lowest vibrational levels of the electronic ground state of BO 2+ has been predicted to be the most efficient decay route of the dication.

Low resolution VUV absorption spectrum of boron monoxide

The absorption spectrum of BO has been recorded between 2400 and 300 Å on the SA61 beam line of SUPERACO in Orsay. A new electronic transition has been observed and vibrationally analysed. Nine Rydberg states have been observed and classified into Rydberg series giving two ionization limits at 12.849eV for the X 1Σ+ ionic state and at 13.117eV for the A 1II state of BO+. Two ionization limits have been observed at 754 and 374 Å. The first of these corresponds to the B 1Σ+ state and the last one to the C 1Σ+ state of BO+. The new results are compared with the ab initio calculations of Karna and Grein concerning BO and BO+. The agreement is satisfactory.

Accurate multireference configuration interaction calculations on the lowest 1Σ+ and 3Π electronic states of C2, CN+, BN, and BO+

Using a series of correlation consistent basis sets from double to quintuple zeta in conjunction with large internally contracted multireference configuration interaction (CMRCI) wave functions, potential energy functions have been computed for the X 1Σ+g and a 3Πu states of C2 and the 1 1Σ+ and 1 3Π states of CN+, BN, and BO+. By exploiting the regular convergence behavior of the correlation consistent basis sets, complete basis set limits have been estimated that led to accurate predictions for the electronic excitation energies, dissociation energies, equilibrium bond lengths, and harmonic vibrational frequencies. The 1 1Σ+ states of CN+ and BO+ are predicted to be the electronic ground states of these species with predicted equilibrium excitation energies (Te) to the low-lying a 3Π states of 880±100 cm−1 and 5000±200 cm−1, respectively. A 3Π ground state of BN is predicted with an excitation energy to the low-lying a 1Σ+ state of just 190±100 cm−1. Identical calculations on the singlet–triplet splitting of C2 yielded a prediction of 778 cm−1 for Te, which was just 62 cm−1 above the experimental value. Accurate equilibrium bond lengths and fundamental frequencies are also predicted for BN, BO+, and the a 3Π state of CN+. Dipole moment functions have been computed by CMRCI for the ground and excited electronic states of the three heteronuclear diatomics, and these have been used to derive accurate microwave and infrared transition probabilities for these species. A dipole moment in v=0 of 5.42 D is calculated for the X 1Σ+ state of BO+, which should lead to an intense microwave spectrum. While the X 3Π ground state of BN is predicted to have a very weak infrared spectrum, this species should be observable in the microwave region since the predicted μ0 is 1.98 D. Both the microwave and infrared spectra of X 1Σ+ CN+ should be of moderate intensity.

Constrained Newton approach adequate to direct self-consistent field calculations in closed- and open-shell configurations

The quadratically convergent approach to solve self-consistent field (SCF) solutions for closed- and open-shell configurations is derived from the Lagrange–Newton method with constraints of the molecular orbital orthonormality. The resulting Lagrangian supermatrix is expressed in a simple manner in terms of atomic orbital (AO) integrals. The present scheme realizes a decrease in computational cost when used with secondary memory to save the Lagrangian supermatrix. Furthermore, the direct SCF approach of the proposed scheme may be efficient to cut down computational cost when used with a preconditioner useful to improve slow convergence in each Lanczos iteration process. The present scheme converges nearly quadratically to a SCF solution when once a good starting point is chosen. The initial estimates of the Lagrange multipliers play a relatively minor role in the convergence rate. As an illustration of the proposed procedure ab initio calculations for the ground and excited states of CO and the ground states of BO and HCN are carried out. The results are compared with those of the Newton–Raphson SCF approach based on the exponential parametrization of orbital rotations.

Configuration-interaction study of low-lying valence states of BO+

Low-lying singlet, triplet and quintet states of BO+ were studied by configuration-interaction methods. The ground state is found to be 1 1Σ+, with 1 3Π only 0·3 eV higher in energy. Many stable states are predicted, similar in structure and ordering to those of BeO and BN. Three Π states, 2 1Π, 2 3Π and 1 5Π, have unusually flat minima at large values of R. Vertical and adiabatic ionization potentials of BO for removal of the 5σ and the 1π electron are given. Dipole moments for the three lowest states of BO+ are also reported.

BO: Low-lying electronic states obtained by configuration-interaction studies

Configuration-interaction studies were performed on low-lying 2Σ +, 2Σ −, 2Π, 2Δ, 4Σ +, 4Σ −, 4Π, and 4Δ states of BO. Sixteen stable states have been found, among them four 3 s B Rydberg states. Spectroscopic constants are compared with those of the four observed states and with theoretical results obtained by others. Particular attention is given to the observed perturbations in the C 2Π state, which can be explained by interaction with 1 2Δ, 1 2Σ −, 3 2Σ +, and other states. Comparison with isoelectronic molecules CN and CO + reveals many similarities.

A theoretical calculation of some low-lying electronic states of BO2 +

The four lower-lying electronic states of the boron dioxide cation BO2 + along with the two first doublet states of BO2 have been studied by ab initio methods at different levels of accuracy. The ground state of BO2 + is of 3Σ g - symmetry and lies at 0·7 eV below the singlet 1Σ g + state. The dipole forbidden transition 3Σ u + ← 3Σ g - exhibits a calculated excitation energy of 1·95 ± 0·2 eV. The 1Σ u + ← 1Σ g + excitation energy is predicted at 1·23 ± 0·2 eV. The vibrational frequencies of BO2 + in both states 3Σ g - and 1Σ g + were also computed. The BO2 + species appears not to be a candidate for the new absorption band centred at 2·03 eV recently reported by Bredohl and Dubois [1].

Studies of chemiluminescence in boron atom reactions with epoxides

Chemiluminescence from the electronically excited A 2H state of BO has been observed in the single-collision reactions of boron atoms with several epoxides. Cross sections for the production of the A 2H state of BO were measured and the vibrational distributions in that state were determined.

Studies of chemiluminescence in boron atom reactions with O2, SO2, N2O, NO2, and H2O2

Chemiluminescence has been observed in the single collision reaction of boron atoms with O2, SO2, N2O, NO2, and H2O2. The experiments were performed in a beam-gas apparatus using photon counting to detect the optical signals. The electronically excited A 2π state of BO was observed in all the reactions. In addition, the BO2(A 2πu) state was observed in the reaction of boron with SO2. Cross sections for the production of electronically excited molecules were determined. These cross sections for the reactions with O2, SO2, N2O, NO2, and H2O2 are, respectively, 0.048, 0.0078, 0.01, 0.023, and 0.005 Å2. In the reactions of boron with SO2 the branching ratio was obtained for the two observed chemiluminescent reaction channels. The vibrational distributions in the electronically excited state of BO were determined in the reactions where the spectra were adequately resolved. Some implications of the results are discussed.

Potential curves of BO and LiO calculated with the complete active space SCF (CASSCF) method

The CASSCF method was applied to compute the potential energy curves for the lowest 2.4Σ +, 2.4Π and 2.4Δ states of BO, and the lowest 2Σ +, 2Π and 2Σ − states of LiO. The curves were obtained for internuclear distances ranging from 2 to 25 au using a medium-sized basis set of CGTOs. The results were compared with previous accurate ab initio calculations and available experimental data. The changes in the wavefunction structure along the potential curves were discussed.

Laser excited fluorescence of the Π vibronic states of BO 2

The Π vibronic states of the X 2Π g electronic state of BO 2 have been studied by laser induced fluorescence. The (0, 0, 0) Π — (1, 0, 0) Π and the (1, 0, 0) Π — (2, 0, 0) Π vibronic bands were pumped with a cw dye laser. The results were used to obtain a new set of parameters for the X 2Π g electronic state. Also, the effect of the Fermi interaction on the (1, 0, 0), (2, 0, 0) and (3, 0, 0) fermiads was investigated.

The optically detected magnetic resonance spectrum of BO 2 in the gas phase

Using 5145 Å radiation from an argon ion laser, microwave optical double resonance transitions have been observed among Zeeman-tuned rovibronic sublevels of the X 2Π state of BO 2. Analysis of the strongest of the observed transitions has permitted a more accurate measurement of the Renner parameter than has previously been possible for the ground state of this molecule.

The radiative lifetimes of the first excited state of BO and BO 2

A pulsed dye laser has been used to study the fluorescence of BO and BO 2 in the gas phase at low pressure. Radiative lifetimes of 87.2 ± 2.6 and 76.3 ± 1.4 ns were obtained for the (000) and (100) levels of BO 2(A 2Π u) and of 131 ± 15 and 103 ± 6 ns for levels v 1 = 1 and 2 of BO(A 2Π). Unlike BO 2(A 2Π u), BO(A 2Π) is strongly quenched by the oxygen carrier.

Alternative Technique for the Calculation of Single-Determinant Open-Shell SCF Functions Which Are Eigenfunctions of S2

The most general possible restriction is developed such that a single-determinant open-shell SCF wavefunction shall be an eigenfunction of S2. A method of satisfying this restriction by partitioning of the variational basis set is given. The method is computationally distinct from the equivalence restriction procedure of Roothaan, but yields results equivalent to it. A pilot calculation on the Σ+2 state of BO is carried out as an explicit example of the new method.

Internuclear potential curves for BO, IO and ClO

RKRV potential energy curves have been calculated for the X 2II and A 2II states of IO; the A 2II state of CIO; and the X 2Σ +, A 2II and B 2Σ + states of BO molecules. By comparing these curves with an empirical potential function, dissociation energies have been assigned tentatively to these electronic states. A perturbation in the A 2II state of BO has been predicted due to the X 2Σ + state.