Two-photon sequential absorption spectroscopy of the E(0+) state of iodine monofluoride

The energy levels of a new state of iodine monofluoride lying 5 eV above the ground state have been measured using the two-photon sequential absorption technique. Eleven vibrational levels of the state were measured. A vibrational and rotational analysis gives the spectroscopic constants as T_e = 41291.96 cm⁻¹, ω_e = 248.76 cm⁻¹, ω_eχ_e = 0.4951 cm⁻¹ and B_e = 0.12920 cm⁻¹. The state has 0⁺ character, and dissociates to I⁺ + F⁻ in the diabatic approximation.     

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.     

On the ground-state properties of the germanium dimer

A theoretical evaluation of the bond length, vibrational frequency and dissociation energy of the Ge₂ molecule is reported. The effective core-potential Hartree—Fock calculations followed by extensive Cl give the following values: R_e = 4.60 bohr, ω_e = 217 cm^?1, D_e = 2.54 eV. These values are discussed and compared with those or previous theoretical work and with the available experimental data.     

Matrix studies of the products of laser vaporization of graphite

Laser vaporization is shown to be an efficient source of ionic species for matrix studies. C₂⁻ and other ions are produced by vaporization of graphite. A new spectrum characterized by T_e = 19732 cm⁻, ω_e′ = 1507±2 cm⁻¹ and ω_e″ = 1360±5 cm⁻¹ is detected and assigned to C₂⁺ or, less probably, to C₃⁻. An efficient vibrational energy transfer between C₂ and C₂⁻ is observed.     

Negative ion photoelectron spectroscopy of teo−

We have recorded the photoelectron spectrum of Te0⁻ using a hot-cathode discharge ion source and a negative ion photoelectron spectrometer. The adiabatic electron affinity of TeO is determined to be 1.697±0.022 eV. The negative ion parameters determined in this work are: (w_e″(TeO⁻) = 690 ± 80 cm⁻¹, r_e″(TeO⁻) = 1.884 ± 0.028 Å. and D_o     

Two-photon absorption spectroscopy of iodine monochloride in the 5 eV region

Two-photon high resolution sequential spectroscopy has been used to excite iodine monochloride from X¹Σ⁺ ground state to the intermediate A³Π₁ state and thence to a final electronic state at 4.82 eV. Vibrational and rotational analyses of this state have been carried out for both isotopic species. For I³⁵Cl, T_e = 38916.0 cm^?1 ω_e = 168.99 cm^?1, ω_ex_e = 0.357 cm^?1 and B_e = 0.05685 cm^?1. The state probably has Ω = 1 in case (c) coupling approximation. It is also shown how to two-photon technique enables rotational line structure of the A ← X transition to be selectively excited for either isotopic species at a resolution of 500000, from an absorption mixture containing natural iodine monochloride plus its iodine dissociation product at equilibrium vapour pressure.     

The absorption spectrum of carbon monoxide in the CO(3Π r,a) state between 215 nm and 285 nm

Bye-beam excitation of a He/CO mixture the CO(³Π _r ,a) state was sufficiently populated to allow the measurement of the absorption spectrum. The (0, 0), (1, 1), (2, 2) and (0, 1) bands of thec ³Π←a ³Π system of CO have been observed and the molecular constantsT _e =92036.0 cm^?1 (for the band head), ω _e =2249.5 cm^?1, ω _e x _e =29.5 cm^?1 have been derived for CO(c). A new electronic state withT _e =91854.3 cm^?1, ω _e =848.4 cm^?1, ω _e x _e =9.8 cm^?1,B _e =1.351 cm^?1, and α _e =0.021 cm^?1 was identified to be a³Σ state. It seems to be very likely that this state is the CO (3pσ,³Σ,j) state discussed in the literature. The results indicate a perturbation of the υ=1 levels of the new state by the CO (c,υ=0) levels. Another strong perturbation is found in the υ=4 levels. The three CO(³Σ,b,υ′=0,1,2)←CO (a,υ″=0) bands were also investigated yielding for CO(b):T _e =83778 cm^?1, ω _e =2335 cm^?1, ω _e x _e =59 cm^?1 andB _e =1.86 cm^?1.     

Quantum chemical DFT calculations of the local structure of the hydrated electron and dielectron

The adiabatic bound state of an excess electron is calculated for a water cluster (H₂O) ₈ ^? in the gas phase using the DFT-B3LYP method with the extended 6-311++G(3df,3pd) basis set. For the liquid phase the calculation is performed in the polarizable continuum model (PCM) with regard to the solvent effect (water, ? = 78.38) in the supermolecule-continuum approximation. The value calculated by DFT-B3LYP for the vertical binding energy (VBE) of an excess electron in the anionic cluster (VBE(H₂O) ₈ ^? = 0.59 eV) agrees well with the experimental value of 0.44 eV obtained from photoelectron spectra in the gas phase. The VBE value of the excess electron calculated by PCM-B3LYP for the (H₂O) ₈ ^? cluster in the liquid phase (VBE = 1.70 eV) corresponds well to the absorption band maximum λ_max = 715 nm (VBE = 1.73 eV) in the optical spectrum of the hydrated electron hydr e _hydr ^? . Estimating the adiabatic binding energy (ABE)e _hydr ^t- in the (H₂O) ₈ ^? cluster (ABE = 1.63 eV), we obtain good agreement with the experimental free energy of electron hydration ΔG ₂₉₈ ⁰ (e _hydr ^? ) = 1.61 eV. The local model (H₂O) ₈ ^2? of the hydrated dielectron is considered in the supermolecule-continuum approximation. It is shown that the hydrated electron and dielectron have the same characteristic local structure: -O-H{↑}H-O- and -O-H{↑↓}H-O-respectively.     

b1Σ+ Emissions from group V–VII diatomic molecules. b 0+ → X1 0+, X2 1 emissions of AsI and SbI

Chemiluminescence from the b 0⁺ → X₁ 0⁺ band system of AsI and of the b 0⁺ → X₁ 0⁺, X₂ 1 systems of SbI in the near-infrared spectral region has been observed in a discharge flow system. Analysis of the spectra led to the spectroscopic constants (in cm^?1) of AsI: ω_e(X₁, X₂) = 257 ± 2, ω_ex_e(X₁, X₂) = 0.82 ± 0.2, T_e(b 0⁺) = 11738 ± 5, ω_e(b 0⁺) = 271 ± 2, ω_ex_e(b 0⁺) = 0.66 ± 0.2, and of SbI: T_e(X₂ 1) = 965 ± 10, ω_e(X₁, X₂) = 206 ± 6, T_e(b 0⁺) = 12328 ± 10, ω_e(b 0⁺) = 211 ± 6. The intensity ratio of the two sub-systems b 0⁺ → X₂ 1 and b 0⁺→ X₁ 0⁺ was found to be ≈0.013 in the case of SbI and ? 0.01 for AsI.     

MRCI study on spectroscopic parameters and molecular constants of the ground state of AsP(X1Σ+) molecule

The potential energy curve (PEC) for the ground state of AsP(X¹Σ⁺) has been investigated by the highly accurate valence internally contracted multireference configuration interaction method in the Molpro2008 program package with the correlation consistent basis set. The PEC is fitted to the analytic Murrrell–Sorbie function (M–S function) from which the spectroscopic constants are determined. The present D_e, B_e, α_e, ω_eχ_e, R_e, and ω_e values are of 4.2823 eV, 0.188622 cm^?1, 0.000749 cm^?1, 1.984427 cm^?1, 2.0194 Å, and 598.60 cm^?1, respectively. In addition, by numerically solving the radial Schrödinger equation of nuclear motion in the adiabatic approximation, the total of 96 vibration states is predicted when the rotational quantum number J = 0. The complete vibration levels, classical turning points, inertial rotation, and centrifugal distortion constants are reproduced. Comparison has been made with recent theoretical and experimental data. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2012     

GRECP/MRD‐CI calculations of spin‐orbit splitting in ground state of Tl and of spectroscopic properties of TlH

The generalized relativistic effective core potential (GRECP) approach is employed in the framework of multireference single‐ and double‐excitation configuration interaction (MRD‐CI) method to calculate the spin‐orbit splitting in the ²P^o ground state of the Tl atom and spectroscopic constants for the 0⁺ ground state of TlH. The 21‐electron GRECP for Tl is used, and the outer core 5s and 5p pseudospinors are frozen with the help of the level shift technique. The spin‐orbit selection scheme with respect to relativistic multireference states and the corresponding code are developed and applied in the calculations. In this procedure both correlation and spin‐orbit interactions are taken into account. A [4,4,4,3,2] basis set is optimized for the Tl atom and employed in the TlH calculations. Very good agreement is found for the equilibrium distance, vibrational frequency, and dissociation energy of the TlH ground state (R_e=1.870 Å, ω_e=1420 cm⁻¹, D_e=2.049 eV) as compared with the experimental data (R_e=1.872 Å, ω_e=1391 cm⁻¹, D_e=2.06 eV). © 2001 John Wiley & Sons, Inc. Int J Quant Chem 81: 409–421, 2001     

The ground-state potential energy function of PO+

The ground-state potential energy function of PO⁺ has been calculated from the set of molecular constants B _e, ω_e, a _i (i = 1, … , 5), R _e, D _e and C₄ in the form of generalized potential energy function previously suggested by us for solving the inverse spectroscopic problem.     

Electron impact and single photon ionization cross sections of neutral silver clusters

Neutral silver atoms and small clusters Ag _n (n=1...4) were generated by sputtering, i.e. by bombarding a polycrystalline silver surface with Ar⁺ ions of 5 keV. The sputtered particles were ionized by a crossed electron beam and subsequently detected by a quadrupole mass spectrometer. In alternative to the electron impact ionization, the same neutral species were also ionized by single photon absorption from a pulsed VUV laser (photon energy 7.9 eV), and the photoionization cross sections were evaluated from the laser intensity dependence of the measured signals. By in situ combining both ionization mechanisms, absolute values of the ratio σ _e (Ag _n )/σ _e (Ag) between the electron impact ionization cross sections of silver clusters and atoms could be determined for a fixed electron energy of 46 eV. These values can then be used to calibrate previously measured relative ionization functions. By calibrating the results using literature data measured for silver atoms, we present absolute cross sections for electron impact ionization of neutral Ag₂, Ag₃ and Ag₄ as a function of the electron energy between threshold and 125 eV.     

SCF ab-initio ground state potential energy surfaces for HCN and HCN−

SCF computations for the ground state potential surfaces of HCN and HCN^? are performed. These calculations predict that the ground state geometry of the radical anion is R_e(CH) = 2.12 bohr, R_e(CN) = 2.33 bohr and the bond angle θ = 121.7°. The calculations also show that the CH bond in HCN^? is much weaker than in HCN and is similar to the CH bond in HCO. The computed electron affinity is ?1.95 eV. Since the minimum on the potential energy curve for the anion is above the neutral curve rapid auto-ionization should occur to HCN and an electron.     

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.     

eaq− hydration energy and photoemission threshold potentials for mercury in contact with aqueous electrolytes

The meaning of the “red limit” potential in photoemission experiments is discussed. For mercury in contact with aqueous electrolytes, the energy of a photoemitted electron at the “red limit” is 0.6 eV higher than the solvation energy of e_aq^?. This difference is attributed to the solvent reorganization energy contribution to the hydration energy of e_aq^?.     

b 1Σ+ Emissions from group V–VII diatomic molecules: bO+ → X1 O+ emission of Pl

Chemilluminescence of the bO⁺ → X₁O⁺ band system of P1 has been observed in a discharge flow system. Thirty-eight bands of the sequences, δν = +2, +1, 0, ?1, ?2 and ?3 were recorded photoelectrically at medium resolution. Evidence is presented that the vibrational numering assigned to the bands in the recently published first analysis of this system has to be modified. The re-analysis leads to the new constants (in cm ^?1) T_e = 11135 ± 5, ω′_e 400 ± 2, ω_e′_e = 1.4 ± 0.3, ω″_e = 372 ±2 and ωχ″_e, 1.4 ± 0.3 for the bO⁺ and χ₁ states, respectively. An upper limit of 0.01 was found for the ratio of the (0.0) band intensifies of the two sub-systems bO⁺ → χ₂ 1 and bO⁺ → χ₁O⁺.     

Theoretical evidence for multiple 3d bondig in the V2 and Cr2 molecules

Calculated CAS SCF potential curves are reported for the ³Σ_g^? state of V₂ and the ¹Σ_g⁺ state of Cr₂. At the CAS SCF level the ³Σ_g^? state of V₂ is calculated to be bound (R_c = 1.77 Å ω_c = 593.6 cm^?1, D_e 0.33 eV) and to involve a triple 3d bond; while the Cr₂ potential curve is not bound but shows a shoulder near the experimental R_e and the wave function shows multiple 3d bonding in this region.     

Wellenmechanische Absolutrechnungen an Molekülen und Atomsystemen mit der SCF?MO?LC?(LCGO) Methode. X. Das Methylkation (CH3)+

The (CH₃)⁺ has been investigated ab initio, taking all 8 electrons into account, using the Allgemeines Programmsystem/SCF ? MO ? LC (LCGO ) Verfahren. After varying the C? H distance and the position of the C atom, it was found that the (CH₃)⁺ ion is planar with a bond distance of R_CH = 2.05 a.u. The force constants (C? H stretching, angular vibration) were computed to be k₁ = 18.9 mdyn/Å, and the associated frequencies to be ω₁ = 3256 cm^?1 and ω₂ = 1526 cm^?1. The ionization energy was found to be I = 25.75 eV. The electron affinity was estimated to be A = 5.4 eV.     

Langmuir probe study of the charged particle characteristics in an analytical radio frequency-glow discharge. Roles of discharge conditions and sample conductivity

The application of a tuned Langmuir probe to the measurement of the charged particle characteristics of electron number density, ion number density, electron energy distribution function, average electron energy and electron temperature, in an analytical radio frequency (r.f.)-glow discharge is described. Studies focus on the roles of discharge operating conditions and plasma sampling position for conductive (copper) and nonconductive (Macor) samples. Based on the data obtained here, apparent differences in plasma characteristics between conductive and nonconductive samples can be reasonably explained. For example, the sputtering of conductive samples results in plasmas with obviously higher electron and ion number densities than the sputtering of nonconductive samples (e.g. n_i = 1.8 × 10¹⁰ cm⁻³ and n_e = 1.5 × 10⁹ cm⁻³ for copper, and n_i = 8 × 10⁹ cm⁻³ and n_e = 5 × 10⁸ cm⁻³ for Macor under the conditions of argon pressure = 4 Torr, r.f. power = 30 W and sampling distance = 4.5 mm). Conversely, nonconductive samples yield electrons with higher energies (average electron energies of 15 and 7.5 eV and temperatures of 6.5 and 3.5 eV respectively for the Macor and copper samples). Lower d.c. bias potentials for the case of sputtering nonconductive samples yield reduced sputtering rates and charged particle densities, though the electrons in the latter case have higher energies and thus improved excitation capabilities. The differences between r.f.- and d.c.-glow discharge optical emission spectra are also discussed relative to reported electron energy characteristics. Studies such as these will lay the ground-work for extensive evaluation of inter-matrix type standardization for r.f.-glow discharge atomic emission spectrometry.