Ã2Σ+ → X̃+Π Emission spectra of the phosphaethyne cations,HCP+ and DCP+

The electron impact excited òΣ⁺ → X?⁺Π emission spectra of HCP⁺ and DCP⁺ have been observed. The spin-orbit split 0-0 band has maxima at 593.7 and 599.0 nm for HCP⁺ and 593.6 and 598.8 nm for DCP⁺. Short progressions in the V₃(CP) vibration are observed. a₀, v₃ and the upper-state lifetime are determined.     

Molecular-beam-laser studies of the states X1Σ+ and A0+ of PbS

By using a molecular-beam apparatus, laser excitation spectra and microwave-optical double-resonance spectra were observed on the electronic states X¹Σ⁺ and A0⁺ of PbS. For the microwave spectra a resolution up to 10 kHz was achieved and microwave two-photon transitions could be detected. All information was combined into single fitting routine including data from other sources. Besides the usual Dunham parameters the fit model takes account of the breakdown of the Born-Oppenheimer approximation and the isotopic field shift. From the field shift of the electronic energy, the vibrational motion and the rotational motion the electron density as a function of the internuclear distance at the Pb nucleus is derived, which allows a more detailed discussion of the electronic structure of the molecule in combination with future quantum-chemical calculations. Additionally it is shown that the variation of the electron density along the vibrational motion at low vibrational levels can be as large as the variation for the electronic transition A0⁺ -X¹Σ⁺ in the case of PbS. The magnetic hyperfine structure of ²⁰⁷Pb is resolved in a molecule for the first time. The coupling parameter of PbS is compared with that of the isovalent molecule TlCl.     

Radiative lifetimes of the CO a′3Σ+, b3Σ+, c3Π, d3Δ and B1Σ+ states. Absolute emission cross sections for t

Radiative lifetimes have been measured for the CO a′³Σ⁺(ν′=4–9), b³Σ⁺(ν′= 0), c³Π(ν′=0), d³Δ(ν′=1–16) and B¹Σ⁺(ν′= 0) states. Our experimental values, arranged in the same order, are 7–10 μs, 56 ns, 16 ns, 3–7.5 μs, 34 ns. Some of these values disagree with the results of previous experiments. To our opinion this is due to an incomplete identification of the emission spectrum in regions where many bands may overlap, dependent on the applied spectral resolution. For the a′Σ⁺?a³Π and d³Δ?a³Π emissions effective cross sections for quenching by CO molecules are given. In connection with the identification of the spectrum, absolute emission cross sections for electrons incident on CO have been measured for the b³Σ⁺?a³Π and c³Π?a₃Π transitions. For an electron energy, corresponding to the maximum of the excitation function we find cross sections of 5.94 (?1.2) × 10^?18 cm² and 0.630 (? 0.13) × 10^?18 cm², respectively.     

The first two excited 1Σg+ states of Cs2

Laser-induced fluorescence Of Cs₂ molecules in the infrared region (4000–9000 cm^?1) has been observed using several exciting wavelengths from an argon-ion laser and from a ring dye laser. Accurate molecular constants for the first two excited ¹Σ_g⁺ electronic states are derived from spectra recorded at high resolution by Fourier transform spectroscopy. Main molecular constants are: (2)¹Σ_g⁺: T_c = 12114.090 cm^?1, ω_e = 23.350 cm^?1, B_c = 7.4.5 × 10^?3 cm^?1, R_c = 5.8316 Å; (3)¹Σ_g⁺: T_e = 15975.450 cm^?1, ω_e = 22.423 cm^?1 , B_e = 8.23 × 10^?3 cm^?1, R_c = 5.5569 Å.     

b 1Σ+ and a 1Δ emissions from group VI—VI diatomic molecules: b0+ → X10+, X21 emissions of TeSe

Near-infrared emissions of the b0⁺ → X₁0⁺, X₂1 band systems of TeSe have been observed in a discharge flow system. Analysis of the spectra yielded T_e values of the X₂1 and b0⁺ states of 1235 ± 5 cm^?1 and 8794 ± 5 cm^?1, respectively, and a vibrational spacing in the b0⁺ state of ω_e(b) = 294 ± 3 cm^?1.     

CAS SCF Cl calculations for the 3Σ−g, 1Σ+g, 3Σ+u, and 5Δu states of Sc2

CAS SCF CI (SD) calculations have been carried out for the ³Σ^?_g, ¹Σ⁺_g, ³Σ⁺_u, and ⁵Δ_u states of Sc₂ using large gaussian basis sets. The ³Σ^?_g, ¹Σ⁺_g, and ³Σ⁺_u states arise from the ²D(4s² 3d¹) + ²D(4s² 3d¹) limit of Sc₂ and are found to be only weakly bound (D_c ≈ 0.06 eV and R_c ≈ 8.0a₀). The ⁵Δ_u state arises from the ²D(4s² 3d¹) + ⁴F(4s¹ 3d¹ 4p¹) atomic limit. This state is found to be strongly bound relative to its limits (D_c ≈ 0.8 eV and R_c ≈ 7.0a₀).     

Level energies and infrared radiative lifetimes of the muonic molecule Heμ+

Energies and radiative lifetimes are calculated for all bound and quasibound levels of the positive muon molecular ion Heμ⁺, together with the tunneling predissociation lifetimes of its quasibound levels. The radiative lifetimes obtained are much longer than the positive muon decay lifetime, so spontaneous (“infrared”) emission will not be a useful diagnostic for the presence of Heμ⁺ or the analogous molecular ions formed by the heavier inert gas atoms.     

The B 2Σ+-X 2Σ+ system of SrF: Precise spectroscopic constants from a combined fit of microwave and sub-doppler optical spectra

Doppler-free polarization spectroscopy has been used to measure 295 lines in the (0.0), (1.1) and (2.2) bands of the B ²Σ⁺-X ²Σ⁺ system of SrF. These optical data were combined with the results of separate microwave measurements of the X ²Σ⁺ state in a weighted least-squares fit. It is shown that the accuracy of spectroscopic constants of the B ²Σ⁺ state is remarkably improved by the reduction of the upper-state—lower-state correlations. A more reliable determination of the vibrational dependence of rotational and spin—rotation parameters became possible.     

The B 2Σ+-X 2Σ+ system of SrF: Precise spectroscopic constants from a combined fit of microwave and sub-doppler optical spectra

Doppler-free polarization spectroscopy has been used to measure 295 lines in the (0.0), (1.1) and (2.2) bands of the B ²Σ⁺-X ²Σ⁺ system of SrF. These optical data were combined with the results of separate microwave measurements of the X ²Σ⁺ state in a weighted least-squares fit. It is shown that the accuracy of spectroscopic constants of the B ²Σ⁺ state is remarkably improved by the reduction of the upper-state—lower-state correlations. A more reliable determination of the vibrational dependence of rotational and spin—rotation parameters became possible.     

Ab initio potential curves for the lowest 1Σ+ and 3Π states of the ion CN+

Ab initio configuration-interaction calculations using a 9s5p|3s2p gaussian basis supplemented with polarization functions are presented for potential curves for the a ¹Σ⁺ and the lowest ³Π state of CN⁺. The two states are very close in energy and calculations at this level do not give an unequivocal indication of the identity of the ground state.     

Ã2Σ+g → X̃2Πu emission band system of dicyanoacetylene radical cation in the gaseous phase

The emission spectrum of the dicyanoacetylene radical cation has been observed in the 580–720 nm wavelength region as a result of low energy electron impact excitation in a crossed-beam arrangement. The band system is attributed to the òΣ⁺_g → X?²Π_u electronic transition by comparison with the photoelectron spectroscopic and calculated data on the states of dicyanoacetylene cation. The frequencies of the three Σ⁺_g vibrational fundamentals in the ground cation state have been deduced from the emission spectrum. The lifetime of the lowest vibrational level of the òΣ⁺_g state of dicyanoacetylene cation was determined to be 13 ± 2 ns. Emission could not be detected from the corresponding states, òΣ⁺, of fluorocyanoacetylene and cyanoacetylene cations, and these results are discussed.     

b1Σ+ and a1Δ emissions from group VI-VI diatomic molecules: b0+ → X10+, x21 emissions of TeO and TeS

Near infrared emissions of the b0⁺→X₁0⁺, X₂1 band systems of TeO and TeS have been observed by chemiluminescence studies in a fast flow system. In both cases the b → X₁ and b → X₂ subtransitions were found to occur with similar intensities. Analysis of the spectra yielded values of the b0⁺ energies T_e of 9966 ^± 10 cm^?1 and 8457 ^± 10 cm^?1 for TeO and TeS, respectively, and vibrational separations ω_e in these states of 726 ^± 10 cm^?1 and 436 ^± 5 cm^?1. The energy splittings of the X₁0⁺ and X₂1 ground state levels were determined to be 789 ^± 10 cm^?1 and 829 ^± 5 cm^?1.     

Rotational analysis of the 201 and 211 bands in the Ã2Σ+-X̃ 2Π spectrum of N2O+

Analysis of new emission spectra of òΣ⁺-X? ²Π in N₂O⁺, including the forbidden components with Δν₂ = 1, have made it possible to locate all four vibronic components of the ν″₂ = 1 manifold. Principal rotational constants and spinvibronic terms are given. A previous estimate of the Renner parameter is revised to a value of ?0.179 ± 0.002.     

Theoretical study of the 2Σu+ and 2Σg+ states of Li2− and Na2−

Ab initio calculations are performed to obtain potential energy curves for the X¹Σ_g⁺ state of Li₂ and Na₂ and the X²Σ_g⁺ and A²Σ_g⁺ states of their anions. The A²Σ_g⁺ M₂^? curves are found to intersect the X¹Σ_g⁺M₂ curves at low energies and are expected to play a major role in the e^? + M₂ → M^? + M process.     

The geometry of the propynol cation,HC3O+

The geometry of a potential interstellar molecule, the propynol cation, HC₃O⁺, is determined by split-valence plus polarization (6-31G*) SCF method with the inclusion of electron correlation effects by third order Møller—Plesset perturbation theory (MP3). The 6-31G* MP3 geometry is: r_e(CO) = 1.125, r_e(CC) = 1.351, r_e(CC) = 1.214, r_e(CH) = 1.078 A, and thus a B_e of 4.421 GHz.     

Laser-induced fluorescence of CsH: The X1Σ+ state dissociation energy

Laser-induced fluorescence of CsH from the A¹Σ⁺ electronic state to the X¹Σ⁺ state was recorded using high-resolution Fourier transform spectrometry. Ground-state vibrational levels were observed from ν″ = 1 to the dissociation limit. These measurements showed anomalies in the X¹Σ⁺ potential energy curve due to the avoided crossing of ionic and covalent potential curves. Accurate molecular constants were derived for the lower X¹Σ⁺ vibrational levels. The observation of a quasibound level gave the first experimental determination of the dissociation energy (in cm^?1): 14802 ? D_c ? 14813.     

Location of the first 3B2 ← 3B+2 transition in phenanthrene

The polarization of the triplet-triplet absorption spectrum of phenanthrene-d₁₀ in the region from 3500 to 8500 A has been recorded. The ³B₂^? state is located at about 4250 Å. The possibility that phenanthrene might be a suitable chromophore for laser dye synthesis is discussed.     

Solubility and Ionic Processes in the Cu X 2? MX ?H2O ( X ?=Cl?, Br?; M +=Li+, Na+, K+, NH4+, Cs+) Systems

 Solubility isotherms in the CuBr₂−MBr−H₂O (M ⁺ = Li⁺, Na⁺, Cs⁺) systems at 298.15 K were measured. The results together with other available literature data for copper chloride and bromide systems were treated by hydration analysis, and comparative discussion of ionic processes taking place in the respective saturated solutions was performed.     

Solubility and Ionic Processes in the Cu X 2? MX ?H2O ( X ?=Cl?, Br?; M +=Li+, Na+, K+, NH4+, Cs+) Systems

Summary.  Solubility isotherms in the CuBr₂−MBr−H₂O (M ⁺ = Li⁺, Na⁺, Cs⁺) systems at 298.15 K were measured. The results together with other available literature data for copper chloride and bromide systems were treated by hydration analysis, and comparative discussion of ionic processes taking place in the respective saturated solutions was performed. Corresponding author. E-mail: jitka@prfdec.natur.cuni.cz Received August 6, 2002; accepted (revised) November 29, 2002 Published online April 3, 2003