The 2v 2, v 1 and v 3 bands of H2 16O

The 2v ₂, v ₁ and v ₃ bands of H₂ ¹⁶O occurring in the region 2930–4255 cm^-1 were studied from a spectrum recorded with a high resolution Fourier transform spectrometer (resolution: 0·005 cm^-1). The set of the observed transitions leads by a least squares method to the determination of very accurate values of the rotational levels belonging to the vibrational states (000), (020), (100), (001). From these levels, using Watson's Hamiltonian, we have obtained respectively 21 and 17 rotational constants for the states (000) and (020).     

Inner-shell excitation of formaldehyde,acetaldehyde and acetone studied by electron impact

Excitation and ionisation of the carbon and oxygen 1s electrons of formaldehyde, acetaldehyde and acetone have been examined by small-angle inelastic scattering of 2.5-keV electrons, with energy resolutions in the range 0.20–0.50 eV FWHM. Features in the electron energy loss spectra below the inner-shell ionisation thresholds have been assigned to transitions to unoccupied valence (π*) and Rydberg orbitals. Broad maxima in the inner-shell continua of all three molecules have been interpreted as resonances associated with transitions to σ*(CO) orbitals. The assignments of the acetaldehyde and acetone spectra have been supported by comparison with those for CH₄ and H₂ CO. The adiabatic first ionisation potential of H₂ NO and H₂ CF have been estimated from the inner-shell spectra of formaldehyde using the equivalent-core analogy.     

Opto-galvanic spectroscopy of some molecules in discharges: NH2, NO2, H2 and N2

The change of the discharge voltage when laser light crossing the discharge is tuned to a molecular transition has been measured. Experiments have been performed in the wavelength region between 570 nm and 620 nm with discharges in NH₃, NO₂, H₂, N₂, O₂ and argon. Transitions from the ground states of NH₂ and NO₂ and transitions from metastable states of N₂ and H₂ have been detected. The spacial dependence of the opto galvanic in a low pressure dc-discharge of H₂ and N₂ has been studied.     

Electron spectroscopy using excited atoms and photons IX. Penning ionization of CO2, CS2, COS,N2O,H2S,SO2, and NO2

The electron spectra resulting from thermal collisions of He* (predominantly 2³S) metastable atoms with the seven triatomic molecules, CO₂, COS, CS², N₂O H₂S, SO₂ and NO₂, are compared with their respective 584-Å photoelectron spectra using a transmission-corrected electron spectrometer. The normalised relative electronic-state transition probabilities for production of ionic states in Penning ionization and photoionization are reported together with energy shifts (ΔE values) for He*(2³S) Penning ionization. The cross-section for Penning ionization to lower states of NO₂⁺ is extremely low as has been observed in other open shell molecules such as NO and O₂.     

Measurements of NH3 in the ν2 = 1 state by a solid-state, photomixing, THz spectrometer, and a simultaneous analysis of the microwave, terahertz, and infrared transitions between the ground and ν2 inversion-rotation levels

In this paper, we report 30 THz measurements of ammonia in its excited, ν₂ = 1, inversion state. These measurements include transition frequencies and pressure shifts (where significant enough to be observed). Included in the data are two forbidden and three ro-inversion transitions, as well as 18 transitions never directly measured before. The measurements were made with an all-solid-state, diode-laser, difference-frequency spectrometer. Using an innovative laser-frequency locking scheme, this spectrometer provided accurately determined and continuously tuned THz-frequencies without requiring accurate knowledge of the absolute laser frequencies. The details of the spectrometer’s frequency calibration is discussed. A global analysis of NH₃ based on the available ground state, ν₂ = 1 state, and ν₂-band transitions was carried out, and the resulting set of recommended molecular effective-Hamiltonian parameters for ammonia is presented. In addition, calculated center frequencies and intensities for all possible transitions up to J = 20 between rotation, inversion, and vibration levels in the ground and ν₂ = 1 states are included as supplementary material.     

The ν9 band of diazirine,H2CN2, by Doppler-limited Fourier transform infrared spectroscopy

The Doppler-limited infrared spectrum of diazirine was recorded using a high-information Fourier transform spectrometer with a resolution of 0.0054 cm^?1. The rovibrational structure of the ν₉ fundamental (CH₂ rocking) at 1124.9144 cm^?1, which is a C-type band, was analyzed in detail with extensive use of spectrum simulation and correlation diagrams. The molecular constants for the upper energy level of this band were obtained from the overall rovibrational assignment of more than 2000 transitions, which cover the region from 1070 to 1220 cm^?1.     

Photoelectron and electronic absorption spectra of SCl2, S2Cl2, S2Br2 and (CH3)2S2

Photoelectron and electronic absorption spectra of SCl₂, S₂Cl₂, S₂Br₂, and (CH₃)₂S₂ have been measured and analyzed. Quantum chemical calculations (CNDO/ 2 and MWH (Mulliken-Wolfsberg-Helmholtz) have been carried out and the electronic structures have been described in terms of molecular orbital theory. The variation in differential photoionization cross-section as a function of incident photon energy and results of MO computations are used to identify ionization bands and assign ground state MO configurations. Suggested ground state electronic structures coupled with computed virtual MO's are used to interpret the visible and near-ultraviolet electronic absorption spectra. The low energy excited states are described as molecular states followed by the initial members of Rydberg series. Calculated oscillator strengths for molecular transitions are in good agreement with those observed experimentally. Quantum defects, δ, for the Rydberg states have been calculated from the Rydberg equation using the adiabatic first ionization potential.     

The vibration-rotation spectrum of DCP: The analysis of the fundamental bands ν1 and ν2, of the overtone band 2ν1, of the summation band ν1 + 2ν3, and of the difference band ν1 - ν2

The vibration-rotation bands ν₁, ν₂, ν₁ - ν₂, ν₁ + 2ν₃, and 2ν₁ have been recorded and analyzed. A simultaneous fit of 395 transitions, including those previously known, was made to obtain improved spectroscopic constant for D¹²CP in 6 different vibrational states.     

Analysis of 2ν2, ν1, and ν3 of H2Se

We have run the high-resolution infrared absorption spectrum of 2ν₂, ν₁, and ν₃ of H₂Se in the region 5.2 to 3.8 μm. We have identified and fitted approximately 520 transitions in 2ν₂, 930 transitions in ν₁, and 620 transitions in ν₃. Included are transitions from the isotopic species containing selenium isotopes 82, 80, 78, 77, and 76. Using Typke's rotational Hamiltonian, we analyzed all isotopic species simultaneously. Ground-state constants were determined from a simultaneous least-squares fit of 879 distinct ground-state combination differences formed from our data and 109 microwave transitions. Upper-state constants were obtained from least-squares fits of our spectral lines analyzing 2ν₂ as a single noninteracting band and analyzing the Coriolis interacting bands ν₁ and ν₃ simultaneously, keeping the ground-state constants fixed.     

New measurements of the microwave spectrum of formamide

New measurements of the microwave spectrum of formamide have been obtained in the frequency range from 49 to 340 GHz using the microwave spectrometer at the Institute of Radio Astronomy of NASU, Kharkov, Ukraine. An analysis of the rotational spectra of the ground, v₁₂, v₉, v₁₁ and 2v₁₂ excited vibrational states of the main isotopic species as well as of the ground states of the ¹³C, ¹⁵N and ¹⁸O substituted species has been carried out using SPFIT/SPCAT programs. The analysis of a strong Coriolis interaction coupling between v₉, v₁₁ and 2v₁₂ vibrational states of formamide has been also fulfilled as well as the analysis of the quadrupole hyperfine structure of the observed transitions. For the first time the quadrupole coupling parameters for the excited vibrational states and for the ¹⁸O substituted species of formamide were determined.     

Lyman transitions of high rovibrationally excited H2, HD and D2 molecules

Energies and probabilities of Lyman transitions of high rovibrationally excited H₂, HD and D₂ molecules have been measured and compared with calculations. The experimental results are obtained from laser-induced fluorescence spectra that have been recorded in the spectral range from 60 500 to 83 500 cm⁻¹, covering 2/3 of the hydrogen Lyman band system. The necessary vacuum-UV radiation is produced by stimulated anti-Stokes Raman scattering, providing a widely tunable radiation source with narrow spectral bandwidth to resolve single Lyman transitions. The highest internal energies of detected hydrogen isotopologues are close to the dissociation limit. This extends the available data base of Lyman transitions from and to higher rotational states (J > 10) of HD and D₂.     

Concentration-dependent electronic structure and optical absorption properties of B-doped anatase TiO2

The concentration-dependent electronic structures and optical properties of B-doped anatase TiO₂ have been calculated using the density functional theory. The calculated results indicate that the electronic structures of B-doped TiO₂ have changed compared with those of pure TiO₂, which is mainly due to the new midgap states induced by B doping. As to the optical properties, we calculate the imaginary part of dielectric function ε₂(ω) and optical absorption spectra of pure and B-doped TiO₂. Two transitions E₁ and E₂ emerged after B doping. The intensity of absorption is enhanced by B doping both in the UV and visible regions. According to the results of imaginary part of dielectric function ε₂(ω) and DOS, it can be concluded that the two optical transitions correspond to the transitions from the O 2p states in the top of valence band to the midgap states and from the midgap states to the Ti 3d states in the bottom of conduction band, respectively. These results have important implications for the further development of photocatalytic materials.     

The microwave spectrum of the PH2 radical

Three rotational transitions, 1₁₀ ← 1₀₁, 2₂₀ ← 2₁₁, and 3₃₀ ← 3₂₁, of the PH₂ radical in the ground vibronic state were observed in the mm-wave region, by using a source-frequency modulation spectrometer with a 1-m-long free space cell. The PH₂ radical was generated directly in the cell by glow discharge in a mixture of phosphine and oxygen. Thirty four fine and hyperfine components were measured for the three transitions. An analysis of the observed spectra, combined with far-infrared and mid-infrared laser magnetic resonance spectra and laser-induced fluorescence spectra obtained by other works, improved the rotational and spin-rotation interaction constants in precision. The observed hyperfine structure gave the magnetic hyperfine coupling constants for both P and H nuclei and also the P nuclear spin-rotation interaction constants.     

Inner shell electron energy loss spectra of the methyl amines and ammonia

Electron energy loss Spectroscopy has been used to obtain the inner shell excitation spectra of the methyl amines CH₃NH₂, (CH₃)₂NH and (CH₃)₃N for both the N 1s and C 1s regions. A spectrum of the N 1s region of NH₃ is also presented at higher resolution than previously published data. The C ls spectra are all very similar and the discrete portions may be assigned to Rydberg transitions. However, features attributable to a σ^* shape resonance are observed just above the N 1s and C ls ionization edges. The NH₃ spectrum is ascribed to Rydberg transitions. The N 1s spectra of the methyl amines, however, become increasingly dominated by a σ* resonance in the continuum with increased methylation. The features in the inner-shell spectra are compared with the reported valence-shell optical absorption spectra and support the Rydberg assignment. The inner-shell spectra of (CH₃)₃N and NH₃ are also compared with previously published inner shell electron energy loss spectra of NF₃ and the third row phosphorus analogues PF₃,P(CH₃)₃andPH₃.     

A coupled gain calculation and output characteristics of the two Ne-like 2s and 2p hole X-ray laser lines

In most collisionally pumped X-ray lasers the lasing transitions considered are a result of collisional excitation of a Ne-like ground state 2p electron into a 3p excited level. However, there are suggestions of producing plasma conditions for collisional pumping of the inner-shell 2s electrons into highly excited 3s levels, with lasing arising as a 2p electron fills the 2s hole. Simulations on various Ne-like ions such as germanium, krypton, and yttrium, using collisional pumping, to get gain on the inner-shell transitions at 62, 50.2, and , respectively, have shown gains on the inner-shell transitions up to . It has been suggested that the large Doppler linewidth associated with shorter wavelengths is responsible for the smallness of the small-signal gain in the inner-shell transitions relative to than that predicted for the more usual 2p-hole transitions. However, experimental investigations of this 2s-hole inner-shell laser line, using collisional pumping technique, were unable to register any output. In this paper we report the result of calculations of the gain and the total spontaneous emission rate for the 2s-hole and the 2p-hole X-ray laser lines using a coupled four level model. It is shown that the small-signal gain of the 2s-hole inner-shell transition decreases with increasing pumping rates of the 2p-hole upper and lower levels. The output characteristics of the Ne-like inner-shell transition is simulated using this four-level model and the effects of saturation of the 2p-hole line on the 2s-hole transition is studied showing that the saturation of the former may have a severe effect on the output of the later.     

Ab initio study of ion-pair states of I2 molecule

This paper reports on ab initio study of the ion-pair states of the I₂ molecule, correlating to I⁺(³ P _{J=2, 1, 0}, ¹ D ₂) + I^?(¹ S ₀) dissociation asymptotes. Calculations are in a rather good agreement with experiment and explain key features of the ion-pair states structure including in particular the remarkable similarity of the gerade state potentials in comparison with the ungerade ones which significantly differ in shape and equilibrium internuclear distance. The dipole moment functions were calculated for the transitions between ion-pair states, correlating to a common and different dissociation thresholds. The dipole moment functions for this type of transitions have been obtained for the first time and are or special interest in the context of resent experimental studies of the amplified spontaneous emission effect on transitions between ion-pair states.     

Multiphoton mass spectra of Xe2 molecules in the range of excited Xe*(6p, 5d) atoms

The (2 + 1) photoionization mass spectra of Xe₂ molecules are studied in a supersonic jet upon excitation by laser radiation in the energy range 80321.3–77821 cm^?1, corresponding to the dissociation of the Xe₂ molecule into atoms Xe(¹ S ₀) + Xe*(6p, 5d). Several vibrational progressions are observed, which are attributed to two-photon transitions of Xe₂ from the ground state to the excited states of the O ⁺ _g, 1_g, and 2_g symmetries. Based on the analysis of these progressions, the molecular constants of a number of excited states of Xe₂ are estimated.     

Collisional transfer of rotational energy in the 2B1 electronic state of nitrogen dioxide

Collisional satellite lines have been observed in fluorescence from nitrogen dioxide excited by the 4545-Å line of the argon laser. The 13_0,13 level of the (0, 8, 0) vibrational state is populated by the laser and undergoes collisionally induced transitions to the 11_0,11, 15_0,15, and 17_0,17 states. These collisionally populated states are identified by their fluorescence to the well-studied (0, 0, 0) and (0, 1, 0) levels of the ground electronic state. These satellite lines are also observed in fluorescence to the (0, 2, 0) and (0, 3, 0) vibrational levels of the ground electronic state. The wavenumbers of those lines, together with those from unrelaxed fluorescence and previously published microwave transitions, allow vibrational and rotational constants for the higher vibrational states to be determined more accurately than was previously possible. Several much weaker forbidden transitions have also been observed, including ΔK_a = 0 through ?6 transitions in the (0, 8, 0)-(0, 0, 1) band.     

Raman line positions in molecular hydrogen: H2, HD,HT, D2, DT,and T2

Spontaneous Raman spectroscopy is used to determine line positions of the six isotopomers of molecular hydrogen: H₂, HD, HT, D₂, DT, and T₂. State populations as low as 1.3 × 10⁸ are detected with the present experimental apparatus. This sensitivity makes possible measurement of the first overtone Q-branch line positions for H₂ and D₂ and of higher rotational transitions than previous investigations. The line positions for D₂, DT, and T₂ indicate that literature values for molecular parameters do not predict accurately line positions of transitions at J values above the observed transitions from which they were determined. The results for the six molecular isotopomers show that ab initio energy levels restricted to the adiabatic approximation do not yield line positions within the experimental uncertainty whereas recent nonadiabatic calculations reproduce the present observations. Reexamination of literature results at high energies indicates discrepancies between the theoretical calculations and experimental vibrational band origins for all vibrational levels in HT, DT, and T₂. No experimental measurements are currently available that test the accuracy of nonadiabatic ab initio rotational levels at high energies.     

Photoabsorption of alloys of Al with transition metals V,Fe, Ni and Cu and Pr near the AlL2,3-edge

The onset of Al 2p transitions of VAl₃, FeAl, NiAl, NiAl₃, CuAl₂, PrAl₂ and the disordered alloys VAl (16 at % Al, 28%, 41%), FeAl (11%) is shifted up to 1.1 eV. New pronounced structure develops close to the onset which for NiAl agrees with a density of states calculation by Connolly and Johnson.