A vacuum ultraviolet laser photoionization and pulsed field ionization study of nascent S(3P2,1,0) and S(1D2) formed in the 193.3 nm photodissociation of CS2

The photoionization efficiency (PIE) and pulsed field ionization-photoion (PFI-PI) spectra for sulfur atoms S(3P2,1,0) and S(1D2) resulting from the 193.3 nm photodissociation of CS2 have been measured using tunable vacuum ultraviolet (vuv) laser radiation in the frequency range of 82 750-83 570 cm(-1). The PIE spectrum of S(3P2,1,0) near their ionization threshold exhibits steplike structures. On the basis of the velocity-mapped ion-imaging measurements, four strong autoionizing peaks observed in the PIE measurement in this frequency range have been identified to originate from vuv excitation of S(1D2). The PFI-PI measurement reveals over 120 previously unidentified new Rydberg lines. They have been assigned as Rydberg states [3p3(4S composite function nd3 D composite function (n=17-64)] converging to the ground ionic state S+(4S composite function) formed by vuv excitations of S(3P2,1,0). The converging limits of these Rydberg series have provided more accurate values, 82 985.43+/-0.05, 83 162.94+/-0.05, and 83 559.04+/-0.05 cm(-1) for the respective ionization energies of S(3P0), S(3P1), and S(3P2) to form S+(4S composite function). The relative intensities of the PFI-PI bands for S(3P0), S(3P1), and S(3P2) have been used to determine the branching ratios for these fine structure states, S(3P0):S(3P1):S(3P2)=1.00:1.54:3.55, produced by photodissociation of CS2 at 193.3 nm.     

Studies on hypersensitive transitions of Nd(III) in Nd(III)-0-diketone-neutral ligand ternary compounds

In this paper, hypersensitive transitions of Nd( I) in Nd( I )-β-diketone-neutra] ligand ternary coordination compounds (where p-diketone = acetylacetone (AA), benzoylacetone (BA), dibenzoylmethane (DBM), 2-thenoyl trifluoroacetone (TTA); neutral ligand = pyridine (Py). cr.a′-dipyridyl (Dipy), phenanthroline (Phen) are studied and their intensities are given through dynamic coupling model. The results are in agreement with those observed and calculated using Judd-Ofelt equation. It may be seen that the dynamic coupling mechanism provides major contribution to the intensity of hypersensitive transition. On the other hand, in order to get the intensity of 4I_9/1→4G_5/2 transition, the absorption spectra in 560–610 nm have been decomposed into three peaks by nonlinear fitting with Lorentzian and Gaussian function and the “pure” intensities of hypersensitive transitions have been obtained, which are agreeable to those computed by Judd-Ofelt method and dynamic coupling model.     

Absolute line intensities for formic acid and dissociation constant of the dimer

Absolute line intensities in the nu(6) and nu(8) interacting bands of trans-HCOOH, observed near 1105.4 and 1033.5 cm(-1), respectively, and the dissociation constant of the formic acid dimer (HCOOH)(2) have been measured using Fourier transform spectroscopy at a resolution of 0.002 cm(-1). Eleven spectra of formic acid, at 296.0(5) K and pressures ranging from 14.28(25) to 314.0(24) Pa, have been recorded between 600 and 1900 cm(-1) with an absorption path length of 19.7(2) cm. 437 integrated absorption coefficients have been measured for 72 lines in the nu(6) band. Analysis of the pressure dependence yielded the dissociation constant of the formic acid dimer, K(p)=361(45) Pa, and the absolute intensity of the 72 lines of HCOOH. The accuracy of these results was carefully estimated. The absolute intensities of four lines of the weak nu(8) band were also measured. Using an appropriate theory, the integrated intensity of the nu(6) and nu(8) bands was determined to be 3.47 x 10(-17) and 4.68 x 10(-19) cm(-1)(molecule cm(-2)) respectively, at 296 K. Both the dissociation constant and integrated intensities were compared to earlier measurements.     

Temperature-dependent luminescence spectra of [ReCl6]2− doped in K2PtCl6-type crystals

Luminescence spectra of [ReCl₆]²⁻ doped in various cubic Rb₂MCl₆ (M = Te, Sn) host crystals have been measured at temperatures between 20 and 240 K. Excitation was obtained at different energy using various laser lines. The intensities of vibronic fundamentals belonging to the Γ₇(²T_2g) → Γ₈(⁴A_2g) transition are compared to theoretical models which describe temperature-dependent transition rates giving rise to vibronic sidebands.     

Errors in isotope ratios measured on a laser mass spectrometer with photographic recording

The random and systematic measurement errors were determined for tin isotope ratios measured by laser mass spectrometry with photographic recording. The analytical isotope signals were treated by the Hull equation using the widths of mass-spectrometric lines. This method significantly reduced the systematic measurement error in the isotope ratios and extended the working range of signal intensities (0.1 <T< 10). Within this range, the relative standard deviation (s _r ) of the measured isotope ratios wass _r < 0.15, and the relative systematic error was S < 0.15. For isotope lines with close signal intensities in the region of normal blackening of the photographic emulsion, the valuess _r = 0.04-0.08 and δ = 0.01 were obtained. A discrimination effect was revealed for isotopes with large masses 120, 122, and 124 amu, which increased δ to 0.21     

Absolute line intensity measurements of hot bands for carbonyl sulfide at 12 microm

Using diode-laser spectroscopy, the intensities of 58 lines of the v(1) + v(1/2) - v(1/2) band and 36 lines of the 2v(1) - v(1) band of OCS have been measured. The corresponding band strengths S(0)(v) and the vibrational transition dipoles micro(v) have been derived through least squares fitting of these individual intensities. The band strengths values have been determined with a precision better than 2.5%.     

Experimental and theoretical studies of small-angle electron scattering by the water molecule

The total (elastic plus inelastic) intensities of 51 keV electrons scattered by water molecules have been measured over a range of 1 ≦ K = (4π/λ) sin(θ/2) ≦ 12 Å^?1. A computer program, ELIC, has been written for calculating the total intensities of electrons scattered by free molecules. The intensities can be calculated with self-consistent field and configuration interaction wavefunctions. The theoretical intensities based on a CI wavefunction are in good agreement with the observed intensities.     

Multiple bonds and re(4f) binding energies of some rhenium halides

Experimental results on the bombardment of some rhenium trihalides by argon ions in a photoelectron spectrometer have yielded lower-valency rhenium halides. The presence of the compounds have been made evident by the destabilization of the Re(4f) and the relative decrease in the halogen spectral line intensities. A theoretical approach to the energy of the Re(4f) states have been studied by the MS X-α method. The molecular model used in the calculations is made up of rhenium polyhalides in D_4h symmetry having the structure Re₂X (n = 2, 4, 6). A discussion is also presented on the formation of multiple bonds as a result of the overlap between the d_xy orbitals of rhenium.     

Systematic LSD investigation on cationic boron clusters: B(n  2–14)

The geometrical structures and properties of small cationic boron clusters B(n = 2–14) have been investigated using the local spin density (LSD ) formalism. The nonlocal correction has also been calculated. The linear search for minima on the potential energy surface has been performed using analytical gradients of the LSD total energy. Most of the final structures of the cationic boron clusters prefer planar or quasi-planar nuclear arrangements and can be considered as fragments of a planar surface or as segments of a sphere. The calculated adiabatic ionization potentials of B_n exhibit features that are analogous to those of measured ionization potentials for boron clusters. Most of the calculated normal modes of the cationic clusters have frequencies that are around 1000 cm^?1 and have strong infrared intensities, and they correspond quite well with analogous properties of solid boron. © 1994 John Wiley & Sons, Inc.     

Small-angle electron scattering by formaldehyde and ketene: Effects of electron correlation and chemical binding

The total (elastic plus inelastic) intensities of 51 keV electrons scattered by H₂CO and H₂CCO have been measured over a range of K = (4π/λ) sin(θ/2) = 1–9.5 Å^?1 and compared with the theoretical intensities calculated with SCF and CI wave functions. Significant discrepancies are found between the experimental intensities and the theoretical ones based on the SCF wave functions. Most of the chemical binding and electron correlation effects observed in the total scattered intensities are reproduced by the theoretical intensities based on the CI wave functions calculated with the basis set including polarization functions on all atoms. © 1992 John Wiley & Sons, Inc.     

A3Pi1u<--X1Sigmag+ laser photoacoustic spectroscopy of Br2 vapor in the extreme red wavelength region 665-720 nm

The A3Pi1u<--X1Sigmag+ photoacoustic spectrum of Br2 vapor has been studied and vibronic analysis performed using earlier data available for this system of bands from optical spectroscopy in the region 665-720 nm. The vibronic levels involved in these transitions are 4< or =v'< or =21 and 1< or =v'< or =4. The relative photoacoustic intensities of the vibronic bands have been used in estimating the non-radiative relaxation rate from vibrational levels of A3Pi(1u) state. The non-radiative relaxation is found to be a nonlinear function of the upper state vibrational quantum number. The radiative rate constants for the A3Pi(1u) state vibrational levels have been compared with the corresponding non-radiative constants obtained from present work. Non-radiative decay rate constants for the vibrational levels of A3Pi(1u) state have been experimentally determined for the first time from photoacoustic spectrum of Br2 vapor in the extreme red region.     

Infrared line collisional parameters of HCl in argon, beyond the impact approximation: measurements and classical path calculations

Measurement of room temperature absorption by HCl-Ar mixtures in the 1-0 and 2-0 bands have been made for pressures between 10 and 50 atm. Fits of these spectra are made for the determination of the width, spectral shift, asymmetry, and intensity of individual lines. The broadening and shifting parameters are in satisfactory agreement with previous determinations but provide the first complete and self-consistent sets covering P(15)-R(14) and P(7)-R(8) in the 1-0 and 2-0 bands, respectively. The asymmetries of the profiles, which have been studied for the first time, are smaller than typically 10(-3) atm(-1) and cannot be determined experimentally. On the other hand, the intensities of the low j lines show a significant linear decrease with increasing Ar pressure. Calculations of all measured quantities are made with a classical path approach and an accurate vibrational-dependent HCl-Ar potential energy surface (PES). Comparisons with experimental values show that widths and shifts are well predicted, confirming the quality of the PES and of the theoretical model, and the calculations confirm that asymmetries are small. The damping factors of the intensities are analyzed by considering three contributions: The first is due to the formation of van der Waals complexes, the second results from the finite duration of collisions, and the last comes from initial correlations. Calculations indicate that the last process has negligible consequences but that the first two processes lead to effects of the same order and explain most of the observed decrease of the intensities, even if some discrepancies persist for the mid R:mmid R:=1 rotational components.     

The application of mass spectrometry to a quantitative characterisation of the electronic and steric effects in organic compounds—I: The transmission of substituent influence through the chain of conjugated double bonds

The mass spectra of polyenic compounds of the type RC₆H₄(CH=CH)_nCOPh, n=1, R=H,p-NMe₂,p-OH,p-OMe,p-Cl,p-Br,p-NO₂,m-NO₂; n=2, R=H, p-NMe₂, p-OMe,p-Cl,p-Br, p-NO₂; n = 3, R = H, p-OMe,p-Cl, p-Br,p-No₂ have been measured. The ratio of the intensities of the common ion PhCO (m/e 105) to the intensities of the molecular ions for these series is correlated with the Hammett-Brown equation with reaction constants p = 0.73 (when n = 1), 0.25 (when n =2), 0.11 (when n = 3). The transmission coefficients were calculated as π'=0.72,0.25 and 0.11 respectively [assuming p=1.01 for benzophenone series-see M. M. Bursey and F. W. McLafferty, J. Am. Chem. Soc. 89 , 1 (1967)]. The contributions of the inductive mesomeric direct polar conjugation and non-additive interaction were calculated in accordance with the equation log Z/Z₀= . It was found that the inductive influence as well as the mesomeric influence of substituents decreases rapidly with the increase in the number of double bonds in the chain. The direct polar effect has a very small value in all series for all substituents with the exeption of NMe₂. Non-additive interaction effects are large. They probably express the general influence of RC₆H₄(CH=CH)_n on COPh.     

Infrared laser absorption spectra of rydberg transitions of O atoms

Many n = 6←5 and 7←6 Rydberg transitions of the oxygen atom have been detected in absorption using infrared diode lasers and twenty-one resolved or partially resolved lines have been accurately calibrated. Line intensities are in agreement with published oscillator strengths. Recent observations on O-atom emission from a laser produced plasma are confirmed.     

Measurement of the sixth overtone band of nitric oxide, and its dipole moment function, using cavity-enhanced frequency modulation spectroscopy

We applied cavity-enhanced frequency modulation absorption spectroscopy (also known as noise-immune cavity-enhanced optical heterodyne molecular spectroscopy) to perform high-resolution spectroscopy of the sixth overtone band of nitric oxide near 797 nm. By using novel high-bandwidth balanced detectors, baseline variations caused by residual amplitude modulation were significantly reduced. The ultrahigh sensitivity (2 x 10(-10) cm(-1) minimum detectable absorption at 1 Hz detection bandwidth) of our spectrometer allowed accurate measurements of 15 individual line intensities of P- and R-branch transitions in the 2Pi(1/2)-2Pi(1/2) subband. A vibrational transition moment of 3.09(6) muD+/-13% and Herman-Wallis coefficients of a = -0.0078(26) and b = 0.001 25(45) were found by fitting the line intensities. Based on our measured transition moment, and those of other transitions from the literature, a new parametrization for the electric dipole moment function (EDMF) of nitric oxide, valid for 0.91 < or = r < or = 1.74 A, has been extracted. The residuals of this fit demonstrate that the derived EDMF is the most accurate representation to date of the dipole moment function. The new EDMF will be valuable for accurate intensity prediction of transitions that cannot be easily measured experimentally.     

The absorption spectrum of water near 750 nm by CW-CRDS: contribution to the search of water dimer absorption

The absorption spectrum of natural water vapour around 750 nm has been recorded with a typical sensitivity of 3 x 10(-10) cm(-1) using a cw cavity ring down spectroscopy set up based on a Ti:sapphire laser. The 13 312.4-13 377.7 cm(-1) spectral interval was chosen as it corresponds to the region where water dimer absorption was recently measured (K. Pfeisticker et al., Science, 2003, 300, 2078-2080). The line parameters (wavenumber and intensity) of a total of 286 lines of water vapor were measured by a one by one fit of the lines to a Voigt profile. For the main water isotopologue, 276 lines were measured with line intensities as weak as 5 x 10(-29) cm molecule(-1)i.e. about 50 times smaller than the weakest H(2)16O line intensities included in the 2004 edition of the HITRAN database. On the basis of the predictions of Schwenke and Partridge, all but 16 lines could be assigned to different isotopologues of water (H(2)16O, H(2)18O, and HD16O) present in natural abundance in the sample. A total of 272 energy levels of H(2)16O were determined and rovibrationally assigned to 18 upper vibrational states. Half of them had not been reported previously. The importance of the additional absorbance resulting from the observation of many new weak lines is discussed in relation to the detection of water dimer absorption and compared to the absorbance predicted by Schwenke and Partridge. The quality of the line parameters of water monomer is shown to be of crucial importance to identify the absorbance of the water dimer in the considered region.     

Eu~(3+)-doped LaPO_4 and LaAlO_3 nanosystems and their luminescence properties

Eu3+ ion-doped LaPO4 nanowires or nanorods have been successfully synthesized by a simple hydrothermal method.The influence of varying the hydrothermal and subsequent sintering conditions on the morphology and structure of the LaPO4 host has been investigated by scanning electron microscopy(SEM) and X-ray diffraction(XRD).For comparison,the Eu3+ ions were also doped into monoclinic monazite LaPO4 nanoparticles and perovskite LaAlO3 nanoparticles.The relative intensities of the emission lines of the LaPO4:Eu...     

Impact of copper vapor contamination on argon arcs

A fast, accurate, and comprehensive emission spectroscopic set-up has been employed to study the impact of copper vapor on an Ar-Cu mixture plasma. Temperature profiles in the arc have been determined in the absence of Cu vapor and then in its presence, using the absolute line intensity method for an Ar spectral line; these profiles have been compared with temperature profiles derived from relative intensities of Cu I lines. Temperature profiles derived from relative intensity of Cu I lines have been used to calculate the radial density distribution of copper atoms in the arc. The following observations have been made from the resulting atomic number densities: (1) the copper vapor concentrates in the fringes of the arc, with atomic number densities up to 8.6×10¹¹ cm⁻³; and (2) Cu atomic number densities in the core of the arc are small.     

Curves of growth of neutral atom and ion lines emitted by a laser induced plasma

The curves of growth of 11 Fe I lines and 10 Fe II lines emitted by a laser-induced plasma have been investigated. The plasmas have been generated with Fe-Ni alloys in air at atmospheric pressure using a Nd:YAG laser. The experimental curves measured at the time windows 1.0–1.5 μs and 3.0–3.5 μs have been reproduced by theoretical curves of growth calculated using a single reduced set of parameters that characterize the plasma, including the apparent temperature, the product N′l of the number density (normalized to 100% concentration) times the length of the plasma along the line-of-sight, and the product αA, which accounts for the perpendicular radiating area of the plasma and the instrumental factor due to the efficiency and the solid angle of the detection system. The plasma apparent (population averaged) temperatures for neutral atom and ion emissions at each time window have been obtained using a modified Boltzmann plot method, based on the replacement of the line intensities by the slopes of the low-concentration limits of the curves of growth, which avoids the systematic error due to self-absorption.