Absolute Line Intensities Research Articles

Spectroscopic density determination of nitrogen species in an ECR discharge

Absolute line intensities of NI up to NV in the VUV region have been measured in an electron cyclotron resonance discharge running in nitrogen and helium-nitrogen mixtures. Using first-order approximation formulae the densities of NI up to NV were determined. For special NII and NIII lines the influence of excitation by inner-shell ionization on density determinations is discussed.

Λ-Splittings and Line Intensities in the 2 ← 1 Hot Band of Nitric Oxide

Using Fourier transform spectra, A-splittings and absolute line intensities have been measured in the 2Π 1/2- 2Π 1/2 and 2Π 3/2- 2Π 3/2 allowed subbands of the vibrational 2 ← 1 hot band of nitric oxide. To retrieve accurate results from the spectra, Λ-doubling and hyperfine splittings were carefully taken into account. However, for most of the studied lines, it turned out that the components of the hyperfine structure are close enough so that they have no susceptible effects on the measured line parameters. Well-chosen cases illustrate the method of measurement. The observed Λ-splittings have been compared with the values deduced from the transition wavenumbers available in the HITRAN database, and large discrepancies (up to 0.006 cm −1 for P(22.5)) appeared for the 2Π 3/2- 2Π 3/2 subband. The measured line intensities led to the determination of the transition dipole moment as well as the Herman-Wallis coefficients for the studied hot band. Our measured intensities have been found to be larger than the HITRAN values by about 7%.

Spectroscopic methods for coronal diagnostics

The EUV spectra present a rich source of information on the nature of the solar corona and the principal means of understanding the underlying mechanisms. Line shifts and broadening give information about the dynamic phenomena in the solar atmosphere and permit a measurement of heating processes (waves, turbulence…). Well chosen line intensity ratios provide knowledge of either the electron temperature or electron density. Absolute intensities of lines corresponding to a large range of temperature give a differential emission measure for the region being viewed and, combined with other physical information, a solution of the density and temperature gradients in that region. These diagnostics are presented and the validity conditions discussed.

Ab initio calculations of the rotationally resolved infrared spectrum of KNa 2 +

Ab initio variational calculations were performed on the rotationally resolved infrared spectrum of KNa2+. A discrete potential energy surface was generated using the configuration interaction ansatz coupled with the frozen core approximation, from which an analytical representation was obtained using a power series expansion employing a Dunham expansion variable. This force field was embedded in an Eckart-Watson rovibrational Hamiltonian, from which eigenfunctions and eigenenergies were calculated. An SCF dipole moment surface was generated and used to calculate absolute line intensities and square dipole matrix elements between the vibrational ground state and the lowest-lying excited states for some of the most intense transitions within the P, Q and R branches.

Enhancement of the vacuum ultraviolet emission from excimer laser-generated plasmas by ambient gas atoms

We have measured the axial (z) and radial (x) distribution of the vacuum ultraviolet emission from excimer laser generated aluminum plasmas in vacuum and in 300 mTorr of argon. The ratio of the radiated line intensities (emission in a gas versus vacuum) on the z axis (i.e., x=0) increased exponentially with distance from the target surface for plasmas generated in a 300 mTorr argon ambient. The absolute line intensities increased linearly with the argon pressure and approximately linearly with the ambient gas atomic cross section when other rare gases were substituted. The line intensity radial distribution was broader for plasmas in argon than in vacuum and the magnitude of the effect increased monotonically with z. The spectral data obtained from plasmas in a gas ambient are discussed in terms of the diffusion of plasma electrons in an ionized gas.

On the Absolute γ-Ray Line Intensities in the Decay of 99Nb and the Branching Ratio in the Decay of 99Zr to 99mNb and 99gNb

Article On the Absolute γ-Ray Line Intensities in the Decay of 99Nb and the Branching Ratio in the Decay of 99Zr to 99mNb and 99gNb was published on September 1, 1993 in the journal Radiochimica Acta (volume 62, issue 4).

Absolute Intensities of Spectral Lines in the Q-Branch of the CH3D at Low Temperature

Abstract We report the absolute intensities of 38 lines of the Q branch of the v2 band of CH3D near 2200 cm−1, obtained at 98.3 K, using a Fourier Transform spectrometer with a resolution of 0.006 cm−1

Theoretical rotational—vibrational spectrum of SiH 2 (X 1A 1 and a 3B 1)

The three-dimensional potential energy and electric dipole moment functions of the X 1A 1 and a 3B 1 states of SiH 2 have been calculated from highly correlated CEPA electronic wavefunctions. The analytic representations of these functions have been used in perturbational and variational calculations of the rotationally resolved absorption spectrum of X 1A 1 SiH 2. In the variational calculations all anharmonicity effects and vibration—rotation couplings have been considered. The equilibrium spectroscopic constants for SiH 2, SiD 2, and SiHD (X 1A 1 and a 3B 1) isotopomers and absolute integrated band intensities are given. The calculated vibrational band origins agree to within 10–40 cm −1 with available gas phase experimental values. It has been shown that due to strong Fermi resonances the 1ν 1 and 2ν 2 bands have almost equal integrated band intensities in the absorption spectrum and overlap with the 1ν 3 band between 1800 and 2300 cm −1. For the most intense transitions absolute line intensities are given. In the electronic ground state of SiH 2 the vibrational band intensities of the fundamental absorption transitions are found to be more intense than the pure rotational transition in the vibrational ground state.

Absolute Rovibrational Line Intensities in the ν 5 Band System of Cyanogen, NCCN

The far-infrared spectrum of the lowest-lying rovibrational band system ν 5 of cyanogen, NCCN, was measured in the wavenumber range from 180 to 280 cm −1. A Fourier transform interferometer was used. Absolute rovibrational line intensities of the fundamental and the first hot band were evaluated. The pure vibrational transition moment matrix elements for the fundamental and the first hot band, |〈μ (00),(01) vib〉| and |〈μ (01),(02) vib〉|, were determined to be 0.1812(19) and 0.1790(30) D, respectively. Furthermore, four nitrogen-broadened spectra of this band system were measured in the pressure range between p N 2 = 8 and 30 mbar (0.1 mbar cyanogen), yielding a nitrogen-broadening coefficient of 0.12 cm −1/atm decreasing slightly with increasing rotational quantum number J. No pressure-induced shifts of line positions were observed in this pressure range. The effects of instrumental distortion on line intensities are discussed.

Absolute Line Intensities for the ν 2 Band of 12CH 3D

Absolute line intensities from the ν 2 fundamental vibration-rotation band of 12CH 3D were measured using an infrared tunable diode laser spectrometer. Selected P- and R-branch lines were studied in the spectral region from 2170 to 2235 cm −1. A squared vibrational transition dipole matrix element was determined to be (8.427 ± 0.220) × 10 −4 (debye) 2 based upon these measured line intensities. Also, an estimate of the ν 2 band intensity of 19.2 (cm −1/cm-atm) was obtained at a temperature of 297.4 K. These parameters compared favorably with previously determined values.

Absolute Line Intensities in the Bands ν2 and ν5 and the Transition Dipole Moments of CH3F

The absolute intensities of 188 vibration-rotational spectral lines of transitions to the vibrational states ν2 = 1 and ν5 = 1 of 12CH3F have been measured with a diode laser. By taking into account the mixing of the rovibrational wavefunctions of both vibrational states by Coriolis and l-type interactions (Papoušek, Papoušková, Ogilvie, Pracna, Civiš, and Winnewisser. J. Mol. Spectrosc.153, 145-166 (1992 )), the values of the vibrational transition moments and their relative signs were determined by a least squares fit to the experimental data: 〈0, 00|μz| 1, 00〉 = ϵ × (0.01106 ± 0.00017)D and〈0, 00|μx|0, 1±1〉 = ϵ × (0.02173 ± 0.00005)D where ϵ = ±1.

Absolute Line Intensities of the ν6 Band of CH335Cl at 10 μm

Strengths of individual lines in the ν6 degenerate fundamental at 10 μm of methyl chloride have been measured at room temperature using a diode laser spectrometer. From these measurements we have determined by a linearized fit two significant intensity parameters, namely, the band strength, Sv0 = 15.06 ± 0.19 cm−2 atm−1 at 297 K and the parameter α = 0.0081 ± 0.0017 of the Herman-Wallis factor F = (1 + αKΔK + ···)2.

Variational calculations of rovibrational states of Li 2K +

The low-lying rovibrational states for the ground electronic state of Li 2K + were calculated using an ab initio variational solution of the nuclear Schrödinger equation. A discrete configuration interaction potential energy surface was generated and an analytical representation was obtained using a power series expansion. This force filed was embedded in the Eckart-Watson Hamiltonian from which rovibrational wavefunctions and eigenenergies were variationally calculated. An SCF dipole moment surface was generated and used to calculate absolute line intensities and square dipole moment matrix elements for some of the most intense transitions within the P, Q and R branches, between the vibrational ground state and the low-lying rovibrational states.

The Fourier transform spectrum of the coloured vibrations in mono- and dideuteroacetylene

The spectral ranges corresponding to 5 v CH and 5 v CD were recorded at high resolution in C 2HD and C 2D 2 respectively, using a Fourier transform interferometer. The rovibrational analysis of the bands is presented, as well as the band strengths derived from the absolute rovibrational line intensities.

The ν3 Fundamental in C2H2

Absolute line positions and intensities are provided for the ν3 fundamental in C2H2 with an accuracy estimated to respectively 6 × 10−4 cm−1 and 0.05 cm−2 atm−1. Unperturbed values are derived for the energy and intensity parameters by treating the Fermi-type resonance and k-doubling effects involved through the interaction with the ν2 + ν4 + ν5 level. The complete set of k-components is included in the procedure. Fitting procedures are carried our on the line energies, the line intensities, and both sets of information simultaneously. The main results are, for the deperturbed values: E(ν3) = 3288.58075(13) cm−1, E(ν2 + ν4 + ν5) = 3296.79650(9)cm−1, k2345 = 25.86749(13) cm−1, and the transition moments Rv(ν3) = ±0.08907(3) D and Rv(ν2 + ν4 + ν5) = ∓2.63(3) × 10−3 D. with the errors (1σ) quoted on the last digits. The mixing between the various levels is quantitatively discussed.

Variational calculations of rotationally resolved infrared properties of Li 2Na +, LiNa 2+ and KLiNa +

Ab initio variational rovibrational calculations have been performed for the ground electronic states of Li 2Na +, LiNa + 2 and KLiNa +. Discrete potential and electric dipole moment surfaces were used to calculate rovibrational transition frequencies, absolute vibrational bands and line intensities. The variational rovibration calculations take into account a full description of the mechanical and electrical anharmonicity as well as vibration—rotation coupling effects. Absolute line intensities and square dipole matrix elements are given for some intense transitions within the P-, Q- and R-branches between the vibrational ground state and the lowest lying excited states.

Quantitative x-ray emission from a DPF device

The x-ray emission was measured from a Dense Plasma Focus (DPF) device. The high density plasma is generated by an electrical discharge in rarefied-neon gas between electrodes in a Mather-type plasma focus configuration. A curved-crystal x-ray spectrograph, a pinhole camera, and an active-filtered photodiode were the diagnostics viewing the axial output of the pinched-plasma region. The x-ray pinhole images indicate a pinched volume roughly 8 mm in length with a nearly circular cross section of about 300 μm in diameter. The digitized spectral traces were computer processed to obtain absolute x-ray line intensities. The neon plasma yielded 10–15 J of K-shell radiation into 4π with the hydrogenlike and heliumlike alpha lines totaling 55%–65% of the total spectral emission. The x-ray emission of the DPF device was studied as a function of discharge current and anode diameter.

Absolute line intensities of the ν9 band of propyne at 15.5 μm

Abstract A tunable diode laser spectrometer was used to perform measurements of absolute line intensities for 20 transitions in the ν 9 -fundamental of propyne centered at 15.5 μm. From these data, the vibrational band-strength S v o was significantly determined to be S v o = 196.8 ± 6.0 cm −2 atm −1 at 297 K. These results will be used for further applications of astrophysical interest such as a refined contribution for modelling Titan's atmosphere.

Vibration-rotational interactions in the states v2 = 1 and v5 = 1 of H 312CF

The vibration-rotational bands ν 2 and ν 5 of gaseous fluoromethane H 3 12CF have been measured in the region 1250–1600 cm −1 with resolution 0.0034 cm −1; the 2046 lines that have been assigned include 85 lines of the Δ k = ±2 perturbation-allowed transitions to the doubly degenerate vibrational state v 5 = 1. A variational approach has been applied to the analysis of both bands which are strongly perturbed by x- y Coriolis interaction and by “2, −1” l-type coupling. Simultaneously with 96 previously reported frequencies of pure rotational transitions in the ground vibrational state and 202 frequencies in the excited vibrational states v 2 = 1 and v 5 = 1 [Pracna, Papoušek, Belov, Tretyakov, and Sarka, J. Mol. Spectrosc. 146, 120–126 (1991)], the wavenumbers of 2046 vibration-rotational transitions of the bands ν 2 and ν 5 have been fitted to determine 7 parameters of the ν 2 band and 21 parameters of the ν 5 band. The ground state parameters A 0 = 5.1820107(12) cm −1 and D K 0 10 −6 = 70.39(15) cm −1 are in excellent agreement with those determined previously [Graner, Mol. Phys. 31, 1833–1843 (1976)]. A standard deviation of 8.0 × 10 −4 cm −1 has been obtained in the simultaneous fit of the infrared data and 0.38 MHz of the rotational frequencies of the upper state, but in the ν 5 band inexplicable systematic differences up to 0.02 cm −1 between the experimental and calculated wavenumbers remain for certain values of the rotational quantum number K at J > 25. From the analysis of the absolute intensities of lines of the ν 2 and ν 5 bands, we found that (∂μ x ∂q 5a )/( ∂μ z ∂q 2 ) = +1.75 , which indicates a negative perturbation of intensity ( ζ 2.5 a y <0).

Asymmetry of Raman scattering at the surface of opaque crystals

For GaAs and GaSb crystals a new type of an asymmetry of the spontaneous Raman scattering (ASRS) is considered. Not only the probabilities of the light scattering are different for the scattering to the right and to the left directions but also the phonon halfwidths differ (the differences for δΩ l and δΩ r can reach 30% in the case of LO phonon lines). In order to describe the experimental results we consider the general case allowing the extinction coefficient to be high. We suggest a scheme for the measurement of impurity concentration in crystals without the measurement of the absolute line intensities. The impurity concentration is defined by the ratio of the phonon halfwidth's δΩ l / δΩ r for the left and right scattering directions.