Electronic states and spin-orbit splitting of lanthanum dimer

Lanthanum dimer (La(2)) was studied by mass-analyzed threshold ionization (MATI) spectroscopy and a series of multi-configuration ab initio calculations. The MATI spectrum exhibits three band systems originating from ionization of the neutral ground electronic state, and each system shows vibrational frequencies of the neutral molecule and singly charged cation. The three ionization processes are La(2)(+) (a(2)∑(g)(+)) ← La(2) (X(1)∑(g)(+)), La(2)(+) (b(2)Π(3/2, u)) ← La(2) (X(1)∑(g)(+)), and La(2)(+) (b(2)Π(1/2, u)) ← La(2) (X(1)∑(g)(+)), with the ionization energies of 39,046, 40,314, and 40,864 cm(-1), respectively. The vibrational frequency of the X(1)Σ(g)(+) state is 207 cm(-1), and those of the a(2)Σ(g)(+), b(2)Π(3/2, u) and b(2)Π(1/2, u) are 235.7, 242.2, and 240 cm(-1). While X(1)Σ(g)(+) is the ground state of the neutral molecule, a(2)Σ(g (+) and b(2)Π(u) are calculated to be the excited states of the cation. The spin-orbit splitting in the b(2)Π(u) ion is 550 cm(-1). An X(4)Σ(g)(-) state of La(2)(+) was predicted by theory, but not observed by the experiment. The determination of a singlet ground state of La(2) shows that lanthanum behaves differently from scandium and yttrium.     

A comprehensive theoretical investigation of the electronic states of Ca2 up to the Ca(4s(2) 1S) + Ca(4s5p 1P) dissociation limit

A theoretical survey of the electronic structure of Ca(2) is presented using two-electron pseudopotentials complemented by core-polarization operators on Ca atoms and multireference configuration interaction/quasidegenerate perturbation theory (MRCI/QDPT) treatment of molecular excited states. The spectroscopic constants of 70 electronic states up to 30,000?cm(-1) above the ground state are determined. This implies all Ca(2) states dissociating up to the Ca(4s(2) (1)S) + Ca(4s5p (3,1)P) dissociation limits. All spin states (singlet, triplet, and quintet) are investigated. The work emphasizes the variety of interactions implying singly valence and lowest Rydberg excited states, doubly excited states generated by atom pairs (3)P(4s4p) + (3)P(4s4p), or (3)P(4s4p) + (3)D(4s3d), 4p3d double excitations asymptotically localized on a single-atom. Zwitterionic Ca(+) + Ca(-) configurations are evidenced and shown to induce specific electronic patterns in (1)Σ(g)(+), (3)Σ(g)(+), (1)Σ(u)(+), (3)Σ(u)(+), (1)Π(g), (3)Π(g), (1)Π(u), and (3)Π(u) symmetry manifolds. They also provide insight for qualitative features (barriers) found for the lower electronic states already investigated in previous publications by other authors.     

VUV Fourier-transform absorption study of the Lyman and Werner bands in D2

An extensive survey of the D(2) absorption spectrum has been performed with the high-resolution VUV Fourier-transform spectrometer employing synchrotron radiation. The frequency range of 90,000-119,000 cm(-1) covers the full depth of the potential wells of the B (1)Σ(u)(+), B' (1)Σ(u)(+), and C (1)Π(u) electronic states up to the D(1s) + D(2l) dissociation limit. Improved level energies of rovibrational levels have been determined up to respectively v = 51, v = 13, and v = 20. Highest resolution is achieved by probing absorption in a molecular gas jet with slit geometry, as well as in a liquid helium cooled static gas cell, resulting in line widths of ≈0.35 cm(-1). Extended calibration methods are employed to extract line positions of D(2) lines at absolute accuracies of 0.03 cm(-1). The D (1)Π(u) and B' (1)Σ(u)(+) electronic states correlate with the D(1s) + D(3l]) dissociation limit, but support a few vibrational levels below the second dissociation limit, respectively, v = 0-3 and v = 0-1, and are also included in the presented study. The complete set of resulting level energies is the most comprehensive and accurate data set for D(2). The observations are compared with previous studies, both experimental and theoretical.     

Renner-Teller and Fermi resonance interactions for the v3=1 and v7=2 vibronic levels in the A2Πu and X2Πg electronic states of HC4H+

The excitation of the v(3) = 1 (σ(g)(+) C-C stretch) and the v(7) = 2 (π(g)(2) C≡C-C bend) modes in the A(2)Π(u) electronic state of diacetylene cations results in Renner-Teller (R-T) and Fermi interactions. The 3(0)(1) and 7(0)(2) vibronic bands in the A(2)Π(u)-X(2)Π(g) transition of HC(4)H(+) have been measured with rotational resolution using cavity ringdown spectroscopy in a supersonic slit jet discharge. The analysis yields T(00) = 20520.828(4) cm(-1), B' = 0.14047(2) cm(-1), and A' = -17.95(1) cm(-1) for the v(3) = 1 and T(00) = 20573.659(4) cm(-1), B' = 0.14018(3) cm(-1), and A' = -11.55(1) cm(-1) for the v(7) = 2 level in the A(2)Π(u) electronic state. A vibronic analysis has been carried out taking into consideration the R-T, spin-orbit, and Fermi resonance interactions between the ν(3) and ν(7) modes. The levels are fitted to the eigenvalues of an appropriate Hamiltonian matrix. This yields the vibrational frequencies ω(3)′ = 811.8 cm(-1) and ω(7)′ = 403.2 cm(-1), Renner parameter ε(7)′ = 0.065, Fermi coefficients W(1)′ = 10.3 cm(-1) and W(2)′ = 5.1 cm(-1), and spin-orbit interaction constant A(SO)′ = -31.1 cm(-1). A corresponding R-T analysis has been carried out for the X(2)Π(g) ground state of HC(4)H(+) using data available in the literature [Callomon, J. H. Can. J. Phys. 1956, 34, 1046]. This gives ω(3)" = 956.2 cm(-1), ω(7)" = 435.4 cm(-1), ε(7)" = 0.028, W(1)" = 7.2 cm(-1), W(2)" = 10.9 cm(-1), and A(SO)" = -33.3 cm(-1).     

Theoretical study of the photodissociation of Li(2)+ in one-color intense laser fields

A theoretical treatment of the photodissociation of the molecular ion Li(2) (+) in one-color intense laser fields, using the time-dependent wave packet approach in a Floquet Born-Oppenheimer representation, is presented. Six electronic states 1,2?(2)Σ(g)(+), 1,2?(2)Σ(u)(+), 1?(2)Π(g), and 1?(2)Π(u) are of relevance in this simulation and have been included. The dependences of the fragmental dissociation probabilities and kinetic energy release (KER) spectra on pulse width, peak intensity, polarization angle, wavelength, and initial vibrational level are analyzed to interpret the influence of control parameters of the external field. Three main dissociation channels, 1?(2)Σ(g)(+) (m = -1), 2?(2)Σ(g)(+) (m = -2), and 2?(2)Σ(u)(+) (m = -3), are seen to dominate the dissociation processes under a wide variety of laser conditions and give rise to well separated groups of KER features. Different dissociation mechanisms for the involved Floquet channels are discussed.     

He2+和He2++分子离子基态和激发态的特性研究

采用SAC/SAC-CI方法在CC-PV5Z基组下, 计算研究了He2+、He2++的基态及低激发态的分子特性, 给出了其基态和一些激发态的势能函数和光谱数据(Be、αe、ωe和ωeχe). 从群论出发推导了相应状态的离解极限；与已有实验结果的He2+(X2Σu+)相比, 计算结果令人满意. 还计算了激发态2Πu、4Σu+和4Πg的结构与光谱数据. 对于He2++, 计算的九个电子态中只有三个态(X1Σg+、1Σg+和1Σu+)属束缚态, 并得到了其光谱常数. 用价键理论模型的不相交规则对He2++基态的势能曲线极大点产生的原因做了较好的分析.     

Vibronic coupling in the A2Π and B2Σ+ electronic states of the NCS radical

The spin-rovibronic energy levels of the A(2)Π and B(2)Σ(+) electronic states of thiocyanate radical have been calculated variationally, using high-level ab initio coupled diabatic potential energy surfaces. Computations up to J = 7∕2 have been performed, obtaining all levels with K ≤ 3 (Σ(1/2),Π(1/2,3/2),Δ(3/2,5/2),Φ(5/2,7/2)), for energies up to 2000 cm(-1) above the A(000)(2)Π(3∕2) level. The available experimental data have been critically reviewed in the light of the theoretical findings.     

Ground state potential energy curve and dissociation energy of MgH

New high-resolution visible emission spectra of the MgH molecule have been recorded with high signal-to-noise ratios using a Fourier transform spectrometer. Many bands of the A 2Pi-->X 2Sigma+ and B' 2Sigma+-->X 2Sigma+ electronic transitions of 24MgH were analyzed; the new data span the v' = 0-3 levels of the A 2Pi and B'2Sigma+ excited states and the v'=0-11 levels of the X 2Sigma+ ground electronic state. The vibration-rotation energy levels of the perturbed A 2Pi and B' 2Sigma+ states were fitted as individual term values, while those of the X 2Sigma+ ground state were fitted using the direct-potential-fit approach. A new analytic potential energy function that imposes the theoretically correct attractive potential at long-range, and a radial Hamiltonian that includes the spin-rotation interaction were employed, and a significantly improved value for the ground state dissociation energy of MgH was obtained. The v'=11 level of the X 2Sigma+ ground electronic state was found to be the highest bound vibrational level of 24MgH, lying only about 13 cm(-1) below the dissociation asymptote. The equilibrium dissociation energy for the X 2Sigma+ ground state of 24MgH has been determined to be De=11104.7+/-0.5 cm(-1) (1.37681+/-0.00006 eV), whereas the zero-point energy (v'=0) is 739.11+/-0.01 cm(-1). The zero-point dissociation energy is therefore D0=10365.6+/-0.5 cm(-1) (1.28517+/-0.00006 eV). The uncertainty in the new experimental dissociation energy of MgH is more than 2 orders of magnitude smaller than that for the best value available in the literature. MgH is now the only hydride molecule other than H2 itself for which all bound vibrational levels of the ground electronic state are observed experimentally and for which the dissociation energy is determined with subwavenumber accuracy.     

Time-resolved study of excited states of N2 near its first ionization threshold

Two-photon, two-color double-resonance ionization spectroscopy combining synchrotron vacuum ultraviolet radiation with a tunable near-infrared (NIR) laser has been used to investigate gerade symmetry states of the nitrogen molecule. The rotationally resolved spectrum of an autoionizing (1)Σ(g)(-) state has been excited via the intermediate c(4) (v = 0) (1)Π(u) Rydberg state. We present the analysis of the band located at T(v) = 10,800.7 ± 2 cm(-1) with respect to the intermediate state, 126,366 ± 11 cm(-1) with respect to the ground state, approximately 700 cm(-1) above the first ionization threshold. From the analysis a rotational constant of B(v) = 1.700 ± 0.005 cm(-1) has been determined for this band. Making use of the pulsed structure of the two radiation beams, lifetimes of several rotational levels of the intermediate state have been measured. We also report rotationally-averaged fluorescence lifetimes (300 K) of several excited electronic states accessible from the ground state by absorption of one photon in the range of 13.85-14.9 eV. The averaged lifetimes of the c(4) (0) and c(5) (0) states are 5.6 and 4.4 ns, respectively, while the b(') (12), c(')(4) (4, 5, 6), and c(')(5) (0) states all have lifetimes in the range of hundreds of picoseconds.     

Time-resolved Fourier transform emission spectroscopy of He/CH4 in a positive column discharge

Time-resolved Fourier transform infrared emission spectroscopy was applied to the study of a pulsed discharge in a He/CH(4) mixture. The dynamics of the formation and decay of acetylene ν(3) (3289 cm(-1)), methane ν(3) (3019 cm(-1)) and ν(1) (2917 cm(-1)), the CH radical electronic ground state X(2)Π(r) (2309-2953 cm(-1)), C(2) Bernath electronic transition B(1)Δ(g)-A(1)Π(u) (3337-3606 cm(-1)), molecular hydrogen emission transitions 5g-4f and 2p-2s, atomic hydrogen, and atomic helium were monitored in the 1800-4000 cm(-1) region. The time profile of the rotational and vibrational temperature of the CH radical was obtained for a 30 μs time interval during and after the discharge pulse. A kinetic model was used for the study of the chemical dynamics of the formation and decay of the individual fragments. The results from the model were compared to the experimental emission spectra.     

Electronic spectroscopy and electronic structure of diatomic TiFe

Diatomic TiFe, a 12 valence electron molecule that is isoelectronic with Cr(2), has been spectroscopically investigated for the first time. In addition, the first computational study that includes the ground and excited electronic states is reported. Like Cr(2), TiFe has a (1)Σ(+) ground state that is dominated by the 1σ(2) 2σ(2) 1π(4) 1δ(4) configuration. Rotationally resolved spectroscopy has established a ground state bond length of 1.7024(3) A?, quite similar to that found for Cr(2) (r(0) = 1.6858 A?). Evidently, TiFe exhibits a high degree of multiple bonding. The vibronic spectrum is highly congested and intense to the blue of 20?000 cm(-1), while two extremely weak band systems, the [15.9](3)Π(1) ← X (1)Σ(+) and [16.2](3)Π(0+) ← X (1)Σ(+) systems, are found in the 16?000-18?500 cm(-1) region. The bond lengths, obtained by inversion of the B(e) (') values, and vibrational frequencies of the two upper states are nearly identical: 1.886?A? and 344 cm(-1) for [15.9](3)Π(1) and 1.884 A? and 349 cm(-1) for [16.2](3)Π(0+). The measured spin-orbit splitting of the (3)Π state is consistent with its assignment to the 1σ(2) 2σ(2) 1π(4) 1δ(3) 2π(1) configuration, as is also found in the ab initio calculations.     

High-resolution observation and analysis of the I(2) (+) A(2)Π(3∕2,u)-X (2)Π(3∕2,g) system

Rotationally resolved absorption spectra of I(2) (+) were recorded in 12 065-13 062 cm(-1) region by employing optical heterodyne velocity modulation absorption spectroscopy. In total, 4054 lines were assigned to 24 bands in the A(2)Π(3∕2,u)-X(2)Π(3∕2,g) system spanning the vibrational levels υ(') = 1-4 and υ(n) (') = 11-19. The assigned lines were globally fitted and an error of 0.003 cm(-1) was obtained. Rotational constants, B(υ), were used to derive equilibrium parameters B(e) (') = 0.03977725(77) cm(-1), a(e) (') = 1.1819(24)×10(-4) cm(-1), r(e) (') = 2.584386(25) A? of the X(2)Π(3∕2,g) state, and B(e) (') = 0.0305787(37) cm(-1), a(e) (') = 1.2353(23)×10(-4) cm(-1), r(e) (') = 2.94758(18) A? of the A(2)Π(3∕2,u) state. Vibrational energies were used to derive ω(e) (') = 239.0397(55) cm(-1), ω(e)x(e) (') = 0.64951(87) cm(-1) of the X(2)Π(3∕2,g) state and ω(e) (') = 138.103(11) cm(-1), ω(e)x(e) (') = 0.45027(34) cm(-1) of the A(2)Π(3∕2,u) state. The A(2)Π(3∕2,u) (υ(n) = 13) state was found to be rotationally perturbed by the a(4)Σ(1/2,u) (-) (υ(n) = 17) state through second-order spin-orbit coupling.     

Spectroscopic analysis of the coupled 1(1)Π, 2(3)Σ+ (Ω = 0-, 1), and b(3)Π (Ω = 0±, 1, 2) states of the KRb molecule using both ultracold molecules and molecular beam experiments

We report the spectroscopic characterization of excited electronic states of KRb by combining spectra from molecular beam (MB) experiments with those from ultracold molecules (UM) formed by photoassociation (PA) of ultracold atoms. Spectra involving the 1(1)Π, 2(3)Σ(+), and b(3)Π states in a strongly perturbed region have been identified. This approach provides a powerful method to identify the vibrational levels of the excited electronic states perturbed globally by neighboring electronic states. This is because the two sets of spectra from the UM and the MB experiments probe the same energy region from very different initial electronic states. The UM experiments utilize high v' levels of the a(3)Σ(+) state with large internuclear separations, while the MB experiments utilize low v' levels of the ground X(1)Σ(+) state with near-equilibrium internuclear separations. Only the Ω = 1 levels of the 2(3)Σ(+) and b(3)Π states are observed in the MB spectra, while the Ω = 0(-), 1 levels of the 2(3)Σ(+) state and the Ω = 0(±), 1, 2 levels of the b(3)Π state are observed in the UM spectra.     

Probing the structural and electronic properties of Ag(n)H(-) (n = 1-3) using photoelectron imaging and theoretical calculations

Structural and electronic properties of silver hydride cluster anions (Ag(n)H(-); n = 1-3) have been explored by combining the negative ion photoelectron imaging spectroscopy and theoretical calculations. The photoelectron spectrum of AgH(-) exhibits transitions from AgH(- 2)Σ(+) to AgH (1)Σ(+) and AgH (3)Σ(+), with the electron affinity (EA) 0.57(3) eV. For Ag(2)H(-), the only observed transition is from Ag(2)H(-) (C(∞v)) (1)Σ(+) to Ag(2)H (C(2v)) (2)A(') and the electron affinity is 2.56(5) eV. Two obvious electron bands are observed in photoelectron imaging of Ag(3)H(-), which are assigned to the transitions from Ag(3)H(-) (C(2v)-T, which means C(2v) geometry with top site hydrogen) (2)B(2) to Ag(3)H (C(2v)-T) (1)A(1) and Ag(3)H (C(2v)-T) (3)B(2). The electron affinity is determined to be 1.61(9) eV. The Ag-H stretching modes in the ground states of AgH and Ag(2)H are experimentally resolved and their frequencies are measured to be 1710(80) and 1650(100) cm(-1), respectively. Aside from the above EAs and the vibrational frequencies, the vertical detachment energies to all ground states and some excited states of Ag(n)H (n = 1-3) are also obtained. Theoretical calculations reproduce the experimental energies quite well, and the results are used to assign the geometries and electronic states for all related species.     

Luminescence measurements of Xe(+) + N2 and Xe(2+) + N2 hyperthermal charge transfer collisions

Luminescence spectra are recorded for collisions between Xe(+)/Xe(2+) and molecular nitrogen at energies ranging from 4.5 to 316 eV in the center-of-mass frame. In the Xe(+) + N(2) collision system, evidence for luminescent charge-transfer products is only found through Xe I emission lines. The most intense features of the luminescence spectra are attributed to atomic N emissions observed above ～20 eV. Intense N(2)(+) A (2)Π(u) - X(2)Σ(g)(+) and B(2)Σ(u)(+) - X(2)Σ(g)(+) radiance is observed from Xe(2+) + N(2) collisions. The B state formation cross section decreases with collision energy until 20 eV, after which it becomes independent of impact energy with an approximate value of 3 ?(2). The cross section for N(2) (+) A (ν > 0) formation increases with energy until 20 eV, after which it remains nearly constant at ～1 ?(2). The N(2)(+) product vibrational distributions extracted from the spectra are non-Franck-Condon for both electronic product states at low collision energies. The distributions resemble a Franck-Condon distribution at the highest energies investigated in this work.     

Rotational analysis and deperturbation of the A2Π → X2Σ+ and B'2Σ+ → X2Σ+ emission spectra of MgH

Deperturbation analysis of the A(2)Π → X(2)Σ(+) and B(')(2)Σ(+) → X(2)Σ(+) emission spectra of (24)MgH is reported. Spectroscopic data for the v = 0 to 3 levels of the A (2)Π state and the v = 0 to 4 levels of the B'(2)Σ(+) state were fitted together using a single Hamiltonian matrix that includes (2)Π and (2)Σ(+) matrix elements, as well as off-diagonal elements coupling several vibrational levels of the two states. A Dunham-type fit was performed and the resulting Y(l,0) and Y(l,1) coefficients were used to generate Rydberg-Klein-Rees (RKR) potential curves for the A (2)Π and the B'(2)Σ(+) states. Vibrational overlap integrals were computed from the RKR potentials, and the off-diagonal matrix elements coupling the electronic wavefunctions (a(+) and b) were determined. Zero point dissociation energies (D(0)) of the A(2)Π and B'(2)Σ(+) states of (24)MgH were determined to be 12,957.5 ± 0.5 and 10,133.6 ± 0.5 cm(-1), respectively. Using the Y(0,1) coefficients, the equilibrium internuclear distances (r(e)) of the A(2)Π and B'(2)Σ(+) states were determined to be 1.67827(1) ? and 2.59404(4) A?, respectively.     

钠分子三重激发态的光谱分析

利用逆向微扰法、 WKB节点法和夫兰克-康登因子相位法等计算方法,分析了Na2分子的23Σg + (ν=15,J=27)→a3Σu +、 23Πg (ν=11,J=11)→a3Σu +和43Πg (ν=12,J=23)→a3Σu +的微扰增强光学-光学双共振实验光谱,计算了23Σg +、 a3Σu +、 23Πg、 43Πg的电子态势能曲线以及相关跃迁的电子跃迁电偶矩,并在此基础上将理论计算的光谱与实验光谱相比较.     

Communication: multistate quantum dynamics of photodissociation of carbon dioxide between 120 nm and 160 nm

UV absorption cross section of CO(2) is studied using high level ab initio quantum chemistry for electrons and iterative quantum dynamics for nuclear motion on interacting global full dimensional potential energy surfaces. Six electronic states-1, 2, 3(1)A(') and 1, 2, 3(1)A(")-are considered. At linearity, they correspond to the ground electronic state X?(1)Σ(g) (+) and the optically forbidden but vibronically allowed valence states 1(1)Δ(u), 1(1)Σ(u) (-), and 1(1)Π(g). In the Franck-Condon region, these states interact via Renner-Teller and conical intersections and are simultaneously involved in an intricate network of non-adiabatic couplings. The absorption spectrum, calculated for many rotational states, reproduces the distinct two-band shape of the experimental spectrum measured at 190 K and the characteristic patterns of the diffuse structures in each band. Quantum dynamics unravel the relative importance of different vibronic mechanisms, while metastable resonance states, underlying the diffuse structures, provide dynamically based vibronic assignments of individual lines.     

Crossed beam reactions of methylidyne [CH(X2Π)] with D2-acetylene [C2D2(X1Σg(+))] and of D1-methylidyne [CD(X2Π)] with acetylene [C2H2(X1Σg(+))

The crossed molecular beam reactions of ground state methylidyne, CH(X(2)Π), with D2-acetylene, C(2)D(2)(X(1)Σ(g)(+)), and of D1-methylidyne, CD(X(2)Π), with acetylene, C(2)H(2)(X(1)Σ(g)(+)), were conducted under single collision conditions at a collision energy of 17 kJ mol(-1). Four competing reaction channels were identified in each system following atomic 'hydrogen' (H/D) and molecular 'hydrogen' (H(2)/D(2)/HD) losses. The reaction dynamics were found to be indirect via complex formation and were initiated by two barrierless-addition pathways of methylidyne/D1-methylidyne to one and to both carbon atoms of the D2-acetylene/acetylene reactant yielding HCCDCD/DCCHCH and c-C(3)D(2)H/c-C(3)H(2)D collision complexes, respectively. The latter decomposed via atomic hydrogen/deuterium ejection to form the thermodynamically most stable cyclopropenylidene species (c-C(3)H(2), c-C(3)D(2), c-C(3)DH). On the other hand, the HCCDCD/DCCHCH adducts underwent hydrogen/deuterium shifts to form the propargyl radicals (HDCCCD, D(2)CCCH; HDCCCH, H(2)CCCD) followed by molecular 'hydrogen' losses within the rotational plane of the decomposing complex yielding l-C(3)H/l-C(3)D. Quantitatively, our crossed beam studies suggest a dominating atomic compared to molecular 'hydrogen' loss with fractions of 81 ± 23% vs. 19 ± 10% for the CD/C(2)H(2) and 87 ± 30% vs. 13 ± 4% for the CH/C(2)D(2) systems. The role of these reactions in the formation of interstellar isomers of C(3)H(2) and C(3)H is also discussed.     

Spectral identification of diffuse resonances in H2 above the n = 2 dissociation limit

The resonance structure in molecular hydrogen above the n = 2 dissociation limit is experimentally investigated in a 1 XUV + 1 VIS coherent two-step laser excitation process, with subsequent ionization of H(n = 2) products. Diffuse spectral features exhibiting widths of several cm(-1) in the excitation range of 118,500-120,500 cm(-1) are probed. Information on angular momentum selection rules for parallel and crossed polarizations, combination differences, the para-ortho distinction, extrapolation from rovibrational structure in the bound region below the n = 2 threshold, and mass-selective detection of H(2)(+) parent and H(+) daughter fragments is used as input. This allows for an assignment of the diffuse resonances observed in terms of (1)Σ(g)(+), (1)Π(g), and (1)Δ(g) states, specified with vibrational and rotational quantum numbers.