New valence and Rydberg states of the P18O molecule

The absorption spectrum of the P¹⁸O molecule has been studied in the region 1650–1800 Å. The upper levels of the transitions are shown to be levels of new ²Π valence, ²Π Rydberg and ²Δ Rydberg states of the PO molecule. Most of the levels are perturbed; some of them are predissociated. The new valence state P²Π corresponds to a regular state of the electronic configuration $\text{σ}{}^2\text{π}{}^3\text{π}{}^{12}$ and the ²Π and ²Δ Rydberg states belong to the 5p, 3d, 4d complex series. Perturbations of the P²Π state are shown to arise from Rydberg ～ Non Rydberg interactions with states of same or different symmetry. The complexity of the interactions does not allow to carry out a deperturbation but a comparison with the data of the P¹⁶O molecule allows to give a vibrational assignment to the levels of the P²Π state.     

Predissociation and Λ-doubling in the even-parity Rydberg states of the nitrogen molecule

Predissociations in the y¹Π_g and $\text{x}{}^1\text{Σ}{}_{\mathrm{g}}{}^{\mathrm{?}}$ Rydberg states of N₂ (configurations $\text{1π}{}_{\mathrm{u}}{}^{\mathrm{?1}}\text{4pσ}$ and $\text{1π}{}_{\mathrm{u}}{}^{\mathrm{?1}}\text{3pπ}$, respectively) and their likely causes, are discussed. Peaking of rotational intensity at unusually low J values, without sharp breaking off, is interpreted as due to case c^? or case cⁱ predissociation. Λ doubling in the y state, attributed to interactions with the $\text{x}{}^1\text{Σ}{}_{\mathrm{g}}{}^{\mathrm{?}}$ state and with another, ¹Σ⁺, state of the same electron configuration as x, is analyzed. From this analysis the location of the (unobserved) ${}^1\text{Σ}{}_{\mathrm{g}}{}^{\mathrm{+}}$ state, here labeled x′, is obtained. It is concluded that the predissociation in the Π⁺ levels of the y state is an indirect one mediated by the interaction with x′ coupled with predissociation of x′ by a ${}^3\text{Σ}{}_{\mathrm{g}}{}^{\mathrm{?}}$ state dissociating to ${}^4\text{S +}{}^2\text{P}$ atoms: combined, however, with perturbation of the y state by the k¹Π_g Rydberg state (configuration $\text{3σ}{}_{\mathrm{g}}{}^{\mathrm{?1}}\text{4dπ}$), whose Π⁺ levels are completely predissociated.     

Rydberg states of the PO molecule

The absorption spectrum of the PO molecule in the region 2100 to 1550 Å has been studied in detail at high resolution. From a rotational analysis of the spectrum, a number of new electronic states have been discovered. Some of these electronic states have been assigned to Rydberg series of the various nl complexes of PO. An upper limit of the ground state dissociation energy has been lowered to 49090 cm^?1 (X²Π, T₀ = 0). Quantum defects are calculated and the first ionization potential of PO is improved to 67 532 cm^?1.     

Low-lying valence and Rydberg states of NS, obtained by configuration-interaction studies

Using double-ζ plus polarization basis sets with diffuse s and p functions on N and S, configuration-interaction calculations were carried out for low-lying valence and Rydberg states of NS. In general, there is good agreement with experimentally obtained spectroscopic constants, and with theoretical results obtained by other groups. The avoided crossing of 2²Σ⁺(C) and 3²Σ⁺(I), and the reported predissociation from low vibrational levels of the C state received particular attention.     

Observed and calculated interactions between valence states of the NO molecule

No perturbation between two valence states of NO has ever been identified, although many valence-Rydberg and several Rydberg-Rydberg perturbations have been extensively studied. The first valence-valence crossing to be experimentally documented for NO is reported here and occurs between the ¹⁵N¹⁸O B²Π (v = 18) and B′²Δ (v = 1) levels. No level shifts larger than the detection limit of 0.1 cm^?1 are observed at the crossings near $\text{J = 6.5 [B}{}^2\text{Π}\text{(F}{}_1\text{) ～ B′}{}^2\text{Δ}\text{(F}{}_2\text{)]}$ and $\text{J = 12.5 [B}{}^2\text{Π}\text{(F}{}_1\text{) ～ B′}{}^2\text{Δ}\text{(F}{}_1\text{)]}$; two crossings involving higher rotational levels could not be examined. Semi-empirical calculations of spin-orbit and Coriolis perturbation matrix elements indicate that although the electronic part of the $\text{B}{}^2\text{Π}\text{～ B′}{}^2\text{Δ}$ interaction is large, a small vibrational factor renders the ¹⁵N¹⁸O B (v = 18) ? B′ (v = 1) perturbation unobservable. Semi-empirical estimates are given for all perturbation matrix elements of the operators $\text{Σ}{}_{\mathrm{i}}\text{a}\text{?}{}_{\mathrm{i}}\text{l}{}_{\mathrm{i}}\text{·s}{}_{\mathrm{i}}$ and $\text{B(L}{}_{\mathrm{\pm }}\text{S}{}_{\mathrm{?}}\text{? J}{}_{\mathrm{\pm }}\text{L}{}_{\mathrm{?}}\text{)}$ which connect states belonging to the configurations $\text{(σ2p)}{}^2\text{(π2p)}{}^4\text{(π}{}^1\text{2p)}$, $\text{(σ2p)(π2p)}{}^4\text{(π}{}^1\text{2p)}{}^2$, and $\text{(σ2p)}{}^2\text{(π2p)}{}^3\text{(π}{}^1\text{2p)}{}^2$.     

A multi-reference CI study of the low-lying valence and Rydberg states of CF3 radical

Highly correlated calculations at the multi-reference configuration interaction levels including singles and doubles excitations (MR-CISD) and extensivity corrections (MR-CISD?+?Q) have been performed to study some low-lying valence and Rydberg states of the CF₃ radical. Our highest level results (at the MR-CISD?+?Q level) yield the following energy ordering: 3s (7.90?eV)?2A₂ (8.61?eV)?π (8.72?eV)?z (8.73?eV). MR-CISD results indicate transitions of similar intensities from the ground to the following three final states, in the following order: 3p_π?>?3p_z?>?3s. It has also been found that the aforementioned Rydberg states should be responsible for visible emissions and correspond to transitions between bound states. Therefore, it is suggested that the lack of vibrational structure in the visible band of parent systems (e.g. CF₃Cl) may be due to a transition from a bound to an unbound state of the parent molecule.     

New procedure for generating valence and Rydberg orbitals

A previously proposed procedure for generating approximate valence, Rydberg, and continuum orbitals from spectral data is extended to two-valence electron systems. Oscillator strengths and photoionization cross sections are reported for the respective 1s²2s² →1s²2s np and 1s²2s²→1s²2s ep transitions of Be, B⁺, C⁺⁺, N⁺⁺⁺, 0⁺⁴, Ne⁺⁶, Mg⁺⁸, Al⁺⁹, and Si⁺¹⁰. Comparisons show a high level of agreement with Hartree-Fock oscillator strengths, but the accuracy of the cross sections is uncertain.     

Coupling of electron orbital motion with rotation in the high Rydberg states of BH

We have applied optical-optical-optical triple resonance spectroscopy to resolve a system of high Rydberg states in BH that serves quantitatively to characterize a fundamental example of electron-orbital-cation core rotational coupling. The third-color ionization-detected absorption spectrum originating from the photoselected 3s B1Sigma+ Rydberg state with vibrational and total angular momentum quantum numbers, v'=1 and N'=0 consists entirely of vibrationally autoionizing resonances for which final N=1 that converge in series to the BH+v+=1 rotational limits, N+=0, 1, and 2. For series with l=1 converging to N+=0 and 2, Rydberg orbital and rotational angular momenta couple to systematically perturb level energies and distribute lifetime in a well-isolated two-channel rotronic interaction that spans hundreds of wave numbers.     

Potential Energies of the Orbitally Degenerate Atmospheric Rydberg Complexes

A method was developed for calculating the vibronic potential energy surfaces (PESs) of atmospheric complexes consisting of orbitally degenerate Rydberg nitrogen and oxygen molecules and the molecules of a neutral medium in the ground electronic state. The degenerate states are formed as a result of l-mixing in the D and E layers of the atmosphere during the periods of increased solar activity. The complexes are populated in the nonequilibrium two-temperature plasma and are responsible for the incoherent additional background radiation in the decimeter (microwave) and terahertz (IR) bands at an altitude of 80–110 km from the Earth’s surface. To describe the interaction of a weakly bound electron with a singly charged molecular ion and a neutral molecule of a gas medium, the formalism of the multichannel quantum defect (MCD) theory was used. Quantum-chemical calculations of the dependences of the scattering lengths, polarizabilities, and quadrupole moments of the main atmospheric molecules N₂ and O₂ on the interatomic distance were performed. The specific features of the behavior of vibronic PESs of Rydberg complexes for large values of the principal quantum number (n ? 1) were analyzed. The vibronic PESs of orbitally degenerate states were constructed. They are necessary for determining the positions and shape of the vibronic minima of the l-mixing cross sections of the N₂ and O₂ Rydberg molecules in the D and E layers of the Earth’s atmosphere, where the delay times of satellite positioning signals should be minimum. The possibility of “quantum chaos” appearing in the Rydberg complexes at sufficiently large n values and angular momenta of the weakly bound electron was noted.     

Rydberg states of SiBr

New uv absorption spectra have been observed for SiBr. Five Rydberg states are identified to the states $\text{(4sσ)}{}^2\text{Σ}{}^{\mathrm{+}}$, $\text{(5sσ)}{}^2\text{Σ}{}^{\mathrm{+}}$, $\text{(4pπ)}{}^2\text{Π}$, $\text{(3dπ)}{}^2\text{Π}$, and $\text{(3dδ)}{}^2\text{Δ}$ by comparison with SiF and SiCl. The ionization potentials of SiCl and SiBr have been determined for the first time, and were 6.82 and 6.67 eV, respectively.     

用ECM方法研究N2分子部分激发态的势能函数!

本文用研究势能函数的新方法-能量自洽法 (energy-consistent-me thod, ECM)研究了N2分子激发态A3∑+u态,B3∏g态,B′3 ∑-u态和W3Δu态的势能,并与曾经常使用的Morse势,Huxley-Murrell-Sorbi e (HMS)势和基于实验的Rydberg-Klein-Rees (RKR)数据进行了比较.结果表明,新的ECM 势能不仅能与基于实验的RKR数据相符合,而且还能得到实验方法难以得到,但在许多研究中又非常重要的渐近区和离解区的势能数据,而在这些区域,过去常用的Morse势和HMS势函数均难以得到正确的势能.因此,ECM势比Morse势和HMS势更加优秀.     

NO2分子里德堡态的光学-光学双共振多光子离化谱

采用光学-光学双共振多光子离化（Optical-optical double-resonant multiphoton ionization，简称OODR-MPI）技术详细研究了NO2分子里德堡态的能级结构。结果显示，用不同强度的激光作抽运光，尽管NO2分子的OODR-MPI谱均由规则的光谱序列组成，但NO2分子的离化通道存在很大区别，当抽运光强度较高时，NO2分子通过(3+1+1)双共振多光子过程离化；而当抽运光强度较低时，NO2分子通过(1+2+1)双共振多光子过程离化，两种离化机制的最终共振能级属于不同的里德堡态。     

Spectroscopy and scattering matrices with nitrogen atom: Rydberg states and optical oscillator strengths

The scattering matrices of ${rm e}+ {rm N}^{+}$ with $J^pi=1.5^{+}$ in discrete energy regions are calculated using the eigenchannel R-matrix method. We obtain good parameters of multichannel quantum defect theory (MQDT) that vary smoothly as the function of the energy resulting from the analytical continuation property of the scattering matrices. By employing the MQDT, all discrete energy levels for N could be calculated accurately without missing anyone. The MQDT parameters (i.e., scattering matrices) can be calibrated with the available precise spectroscopy values. In this work, the optical oscillator strengths for the transition between the ground state and Rydberg series are obtained, which provide rich data for the diagnostic analysis of plasma.     

Potential energy surface of the Rydberg states of the NO molecule in an intense IR radiation field

A method taking into account valence (non-Rydberg) and dissociative configurations has been developed for calculation of potential energy surfaces of the NO molecule in an intense IR radiation field. The resonance rovibronic structure of the Rydberg molecule–laser field quantum system has been analyzed within the steady-state formalism of the radiation collision matrix using multi-channel quantum defect theory. Special conditions for field control of predissociation involving intermediate Rydberg and valence states have been formulated.     

Oscillator strengths of the vibrational and Rydberg transitions in the 1s absorption spectrum of a nitrogen molecule

Spectral dependences of the total absorption cross sections in the region of the 1s ionization threshold of molecular nitrogen are determined for the first time with a high energy resolution using synchrotron radiation from the Russian-German channel of the BESSY II electron storage ring and continuous radiation from an x-ray tube. For N₂, partial N1s absorption cross sections are derived and the oscillator strengths for the vibrational and Rydberg transition series are evaluated from the measurements carried out with due account of the background and instrumental distortions.     

A predissociative triplet Rydberg state of the nitrogen molecule studied by near-infrared diode laser kinetic spectroscopy

A new ³Π-³Σ band was observed in a discharge plasma of the nitrogen molecule and helium using near-infrared diode laser kinetic spectroscopy. All the lines in this band exhibited line broadening of more than 0.1 cm⁻¹. Rotational analysis revealed that the lower state of the transition was the state of N₂, which had already been studied in the D³Σ-E³Σ band. The term value and rotational constant suggested that the upper state is the G³Π_u Rydberg state with an electron configuration of (N₂⁺:X²Σ core)(3pπ_u). The line broadening is attributed to predissociation through a homogeneous interaction with a repulsive Π_u state.