Fourier spectrometry investigation of the 1 3Σg+ →a 3Σu+ transition of the 7Li2 molecule

The 1 ³Σ_g⁺ → a ³Σ_u⁺ transition in the ⁷Li₂ molecule has been observed in the 8200–10 000 cm⁻¹ region with a high resolution Fourier spectrometer. Rotational analysis of 1 ⩽ υ′ ⩽ 7 of 1 ³Σ_g⁺ and 0 ⩽ υ″ ⩽ 7 of a ³Σ_u⁺ has been carried out. We found D_e(a ³Σ_u⁺) = 332.5 ± 1.0 cm⁻¹ that gives T_e(a ³Σ_u⁺) = 8184.3 ± 1.5 cm⁻¹ and D_e(1 ³Σ_g⁺) = 7090.4 ± 1.5 cm⁻¹ with T_e = 16330 ± 2 cm⁻¹.     

Adiabatic corrections for thei 3Π g state of the hydrogen molecule

Summary The adiabatic corrections of thei ³_g state of H₂ are calculated for a wide range of internuclear distances using an explicitly correlated wavefunction. The vibrational structure of this state is calculated in the adiabatic approximation. It is shown that forN=1 levels of the – substate, for which the nonadiabatic corrections are negligible, the agreement between theory and experiment is excellent; the small mass independent discrepancy of the order of 0.5–3 cm^–1 is due to the convergence error in the Born-Oppenheimer calculations. For higherN the discrepancy is much larger. However, it is mass andN-dependent and it is almost entirely due to the nonadiabatic effects caused by³_g-³_g interactions. The still larger discrepancy for the + substate of thei state is evidently caused by additional interactions of thei state with close-lying states of³ _g ⁺ symmetry.Dedicated to Prof. Klaus Ruedenberg on the occasion of his 70th birthday     

Rotationally resolved (3 + 1) rempi of H 2 via the B1Σ+u state

In the paper, we compare the results of our ab initio calculations for the ro-vibrational branching ratios resulting from a (3+1) REMPI of H₂ via the B¹Σ⁺_u state with the experimental data of Pratt, Poliakoff, Dehmer and Dehmer. These results indicate that non-Franck-Condon effects are less important here than in the (3+1) REMPI of H₂ via the C¹Π_u state. We observe that the ΔJ = ±3 peaks in the photoelectron spectrum are of negligible strength and that the ratio of ΔJ = +1 to ΔJ = −1 peak is independent of the ionic vibrational state. A detailed analysis indicates that these features arise as a result of a dynamic interference between the do and dμ ionization channels and do not imply either the smallness of the d-wave or the smallness of the j_t = 3 angular momentum coupling terms.     

Optical-optical double-resonance spectroscopy of high vibrational levels of the Na2 A 1Σu+ state in a molecular beam

High vibrational bands of the Na₂ A-X system are investigated in a molecular beam by two-step excitation at separate interaction regions. With a first laser A-state levels are optically pumped; they decay radiatively and populate high vibrational levels of the ground state (e.g. υ′' = 31). A second laser excitation starting from these prepared levels allows the investigation of high vibrational levels of the A state, for example υ′ = 66, 67, 68, 69 and υ′ = 70. From analysis of the υ′ = 66, …, 70-υ′' = 31 bands we obtain B(υ) and G(υ) and, including the data of others, we determined a new RKR potential curve for the A ¹Σ_u⁺ state, extending the experimentally determined potential from υ′ = 44 to υ′ = 70 (78% of the well depth).     

The predissociation of Li2 b3Πu by a3Σ+u

⁶Li₂ 1³Δ_g(F₁) → b³Π_u(F₁v = 0–11) rotationally resolved fluorescence spectra are recorded following perturbation-facilitated optical—optical double resonance excitation of 1³Δ_g via spin—orbit mixed A¹Σ⁺_u ∼ b³Π_u(F₁e) intermediate levels. The f-symmetry Λ-components of b³Π_u(F₁) are broadened above the 0.05 cm⁻¹ detection threshold owing to predissociation by the vibrational continuum of the a³Σ⁺_u state. The observed v = 0–11, N = 31f level widths were used to determine the potential energy curve for the Li₂ a³Σ⁺_u state in the region 2.35 < R < 2.60 Å and 11200 < E < 14900 cm⁻¹ (relative to E = 0 at the minimum of X¹Σ⁺_g). The a³Σ⁺_u ∼ b³Π_u curve crossing is at R = 2.57 Å and E = 11246 cm⁻¹ and the electronic part of the − BN·LL-uncoupling matrix element is 〈b Π¦L⁺ ¦aΣ〉 = 1.216H at an R-centroid Rv_bϵ_a = 2.61Å.     

Bond functions in molecular excited states: MRD CI calculations for the A3Σ+u,B3Πg and W3Δu states of N2

Using double-zeta plus polarization (DZP) basis sets systematically augmented with a variety of bond functions, the term dissociation energies are calculated for the A³Σ⁺_u, B³Π_g and W³Δ_u states of N₂. It is found that the best agreement with literature values is generally with a basis set composition of DZP augmented by a set of s, p and d orbitals at the bond midpoint. The excited state potential energy curves and spectroscopic constants for the B³Π_g state are calculated from this basis and compared with experimental values. Good agreement was obtained, considering the small basis set size, with the spectroscopic constants ω_e, ω_eχ_e, ω_ey_e, B_e and α_e and the dissociation energy D_e (e.g., D_e = 3.38 (3.681, exp.), 4.75 (4.897) and 4.77(4.873) eV for the A, B and W stages, respectively). Poorer agreement was obtained for the term energy T′₀ (7.92 versus 7.35 eV, exp., for the B state). The error in term energy arises largely from an error in the calculated ⁴S → ²D splitting (2.705 versus 2.383 eV, exp.), and shifting the potential curve for the B state by a constant amount leads to much improved agreement relative to the ground state. The counterpoise correction applied to the potential curve of the B state causes a drastic deterioration of the results and shows qualitatively incorrect behaviour, and is therefore not recommended for calculations of this type.     

Theoretical study on the singlet and triplet potential energy surfaces of NH (X3Σ−) + HCNO reaction

Both the singlet and triplet potential energy surfaces (PESs) of the NH (X³Σ^?) + HCNO reaction have been investigated at the BMC-CCSD level based on the UB3LYP/6-311++G(d, p) structures. The results show that the title reaction is more favorable through the singlet potential energy surface than the triplet one. For the singlet potential energy surface of the NH (X³Σ^?) + HCNO reaction, the most feasible association of NH (X³Σ^?) with HCNO is found to be a non-barrier nitrogen-to-carbon attack forming the adduct a (trans-HNCHNO), which can isomerize to the adduct b (cis-HNCHNO). The most feasible channel is that the 1, 3-H shift with N2–H2 and C–N1 bonds cleavage associated with the N1–H2 bond formation of adduct a leads to the product P ₁ (HCN + HNO). Moreover, P ₂ (HNC + HNO) should be the competitive product. The other products, including P ₃ (NH₂ + NCO) and P ₄ (N₂H₂ + CO), are minor products. The product P ₁ can be obtained through two competitive channels Path 1: R → a → P ₁ and Path 3: R → b → d → P ₁ , whereas the product P ₂ can be formed through Path 2: R → b → d → P ₂ . At high temperatures, the nitrogen-to-nitrogen approach may become feasible. For the triplet potential energy surface of the NH (X³Σ^?) + HCNO reaction, the Path 10: R → ³ a → ³ a ₁ → P ₁ should be the most feasible pathway due to the less reaction steps and lower barriers. These conclusions will have impacts on further experimental investigations.     

A study of the perturbations between the A1Σ+u and b3Πu states of Na2

The interaction between the A¹Σ⁺_u and b³Π_Ωu states of Na₂ is explored by resonantly exciting A states via A-X transitions and, after an adjustable delay time, photoionizing them. For long delays signals arise only from states with significant fractions of both A and b state character. Thus the regions where the interaction is important stand out clearly in the spectrum. Using this technique we have investigated perturbations of the A v' = 3, 7 and 8 states by the b v' = 10, 13 and 14 states.     

Polarographic catalytic wave of hydrogen——Parallel catalytic hydrogen wave of bovine serum albumin in the presence of oxidants

A polarographic catalytic hydrogen wave of bovine serum albumin (BSA) at about -1.80 V (vs. SCE) in NH4CI-NH3 · H2O buffer is further catalyzed by such oxidants as iodate, per-sulfate and hydrogen peroxide, producing a kinetic wave. Studies show that the kinetic wave is a parallel catalytic wave of hydrogen, which resulted from that hydrogen ion is electrochemically reduced and chemically regenerated through oxidation of its reduction product, atomic hydrogen, by oxidants mentioned above. It is a new type of poralographic catalytic wave of protein, which is suggested to be named as a parallel catalytic hydrogen wave.     

Rovibrational dynamics of the strontium molecule in the A(1)Σ(u)+, c(3)Π(u), and a(3)Σ(u)+ manifold from state-of-the-art ab initio calculations

State-of-the-art ab initio techniques have been applied to compute the potential energy curves for the electronic states in the A(1)Σ(u)(+), c(3)Π(u), and a(3)Σ(u)(+) manifold of the strontium dimer, the spin-orbit and nonadiabatic coupling matrix elements between the states in the manifold, and the electric transition dipole moment from the ground X(1)Σ(g)(+) to the nonrelativistic and relativistic states in the A+c+a manifold. The potential energy curves and transition moments were obtained with the linear response (equation of motion) coupled cluster method limited to single, double, and linear triple excitations for the potentials and limited to single and double excitations for the transition moments. The spin-orbit and nonadiabatic coupling matrix elements were computed with the multireference configuration interaction method limited to single and double excitations. Our results for the nonrelativistic and relativistic (spin-orbit coupled) potentials deviate substantially from recent ab initio calculations. The potential energy curve for the spectroscopically active (1)0(u)(+) state is in quantitative agreement with the empirical potential fitted to high-resolution Fourier transform spectra [A. Stein, H. Kno?ckel, and E. Tiemann, Eur. Phys. J. D 64, 227 (2011)]. The computed ab initio points were fitted to physically sound analytical expressions, and used in converged coupled channel calculations of the rovibrational energy levels in the A+c+a manifold and line strengths for the A(1)Σ(u)(+)←X(1)Σ(g (+) transitions. Positions and lifetimes of quasi-bound Feshbach resonances lying above the (1)S(0) + (3)P(1) dissociation limit were also obtained. Our results reproduce (semi)quantitatively the experimental data observed thus far. Predictions for on-going and future experiments are also reported.     

Analysis of the long range potentials of the X 1Σ+ and a 3Σ+ states of NaK

The difference in energy between the singlet and triplet states of NaK dissociating to Na(3s) and K(4s) is found from experimental data and from pseudopotential calculations. The contributions of various one- and two-electron integrals are evaluated, illustrating the present ambiguity over the exchange integral and the exchange interaction terms.     

An ab initio study of the E 3Πg state of the iodine molecule

The E (3)Π(g) state of the iodine molecule is studied by ab initio multireference methods coupled with effective core potentials and large basis sets. Two potential minima are found, a global featuring an ion-pair character, and a local presenting a purely Rydberg nature. Four avoided crossings along the dissociation coordinate attribute an interesting topology to its potential energy curve, and their effect on the vibrational levels of I(2) is discussed.     

Non-adiabatic effects on oxygen atom fine structure populations in the predissociation of the A2Σ+ state of OH

Multichannel scattering calculations are used to evaluate the role of non-adiabatic interactions and interference effect on the predissociation linewidths of several vibrational levels of the A²Σ⁺ state of OH due to coupling to three different repulsive electronic states. Oxygen atom fine structure branching ratios are calculated as a possible probe of the predissociation pathway. Non-adiabatic effects are found to be very strong for the lower vibrational predissociative A²Σ⁺ levels and to remain non-negligible even for the higher vibrational states of A ²Σ⁺.     

The X1Σ+ ground state of kh near the dissociation limit

Fluorescence excited in the A¹Σ⁺ -X¹Σ⁺ system of ³⁹KH by the 4880 Å argon-ion laser line gives information about the ground state as far as the last bound rovibrational level. This is identified as J = 6 in v = 23, and, assuming a limit midway between J = 6 and J = 7, D_e(KH) = 14776 ± 4 cm⁻¹.     

The (1) 3Σg+ electronic state of Cs2

Laser-induced fluorescence of Cs₂ molecules, recorded by high-resolution Fourier spectroscopy, has been used for the first spectroscopic identification of the lowest gerade triplet (1) ³Σ_g⁺ electronic state. This state can be described by the molecular parameters: T_e = 11602.10 cm⁻¹, B_c = 8.258×10⁻³ cm⁻¹, D_c = 2.56×10⁻⁹ cm⁻¹ and R_c = 5.5425 Å. Determination of the absolute vibrational numbering will require further experiments.     

Formation of ultracold Rb2 molecules in the v' = 0 level of the a(3)Σ+(u) state via blue-detuned photoassociation to the 1(3)Π(g) state

We report on the observation of blue-detuned photoassociation in Rb(2), in which vibrational levels are energetically above the corresponding excited atomic asymptote. (85)Rb atoms in a MOT were photoassociated at short internuclear distance to levels of the 1(3)Π(g) state at a rate of approximately 5 × 10(4) molecules s(-1). We have observed most of the predicted vibrational levels for all four spin-orbit components; 0(+)(g), 0(-)(g), 1(g), and 2(g), including levels of the 0(+)(g) outer well. These molecules decay to the metastable a(3)Σ(+)(u) state, some preferentially to the v' = 0 level, as we have observed for photoassociation to the v' = 8 level of the 1(g) component.     

Alignment effect of N2(A3Σu+) in the energy transfer reaction of aligned N2(A3Σu+) + NO(X2Π) → NO(A2Σ+) + N2(X1Σg+)

Steric effect in the energy transfer reaction of N(2)(A(3)Σ(u)(+)) + NO(X(2)Π) → NO(A(2)Σ(+)) + N(2)(X(1)Σ(g)(+)) has been studied under crossed beam conditions at a collision energy of ~0.07 eV by using an aligned N(2)(A(3)Σ(u)(+)) beam prepared by a magnetic hexapole. The emission intensity of NO(A(2)Σ(+)) has been measured as a function of the magnetic orientation field direction (i.e., alignment of N(2)(A(3)Σ(u)(+))) in the collision frame. A significant alignment effect on the energy transfer probability is observed. The shape of the steric opacity function turns out to be most reactive at the oblique configuration of N(2)(A(3)Σ(u)(+)) with an orientation angle of γ(v(R)) ~ 45° with respect to the relative velocity vector (v(R)), which has a good correlation with the spatial distribution of the 2pπ(g)* molecular orbital of N(2)(A(3)Σ(u)(+)). We propose the electron exchange mechanism in which the energy transfer probability is dominantly controlled by the orbital overlap between N(2)(2pπ(g)*) and NO(6σ).