Pressure-induced shift and broadening of acetylene lines in the region 6580-6600 cm-1

Highly accurate measurements of pressure shift and broadening parameters of acetylene absorption lines in the region 6580-6600 cm-1 have been performed by tunable diode laser spectroscopy (TDLS). For these purposes the three channel spectrometer with distributed-feedback diode laser, operated at 1.53 microm was used. The laser is generating pulses of 4-10 ms duration at a repetition frequency of 40 Hz. A temperature-stabilization system, using a thermoelectric cooling unit affords a temperature stability of the order of 10(-4)K in the temperature range from -15 to +50 degrees C. A three channels acquisition system ensured simultaneous real time recording of the sample gas absorption spectrum and of two spectral calibration signals (Fabry-Perot fringes and low-pressure reference lines). We have measured the pressure-induced self-shift and broadening coefficients for six lines of the R-branch in the nu1+nu3 rotation-vibration band of acetylene 12C2H2. The self-shift coefficients have been determined for these lines in the wide pressure region. A non-linear behavior of the pressure dependence of the shift was observed. The temperature exponent n of pressure-induced broadening and shift are reported.     

Interferometric measurements of atomic line profiles emitted by hollow-cathode lamps and by an acetylene-nitrous oxide flame

Source line profiles for eighteen atomic transitions of nine elements emitted by low-current hollow-cathode lamps and by an acetylene-nitrous oxide flame have been measured with a Fabry-Perot interferometer. Distortions caused by instrument broadening are shown to be negligible. Contribution of self-absorption to the profile widths is estimated. In nearly all cases hyperfine structure has a decisive influence upon the observed profile. For thirteen transitions of known hyperfine structure the experimental curves are compared with computer simulated spectra using Gaussian functions to derive the Doppler temperature of hollowcathode lines and Voigt functions to calculate the collision broadening of flame lines. The results show that the Doppler temperatures of hollow-cathode lines range from 400 to 700°K, that flame lines are significantly shifted to the red and that collision broadening in the flame is fully comparable to Doppler broadening, i.e. the a-parameter varies between 0.5 and 1.5.     

Radical anions of flavonoids

Several representatives of natural flavonoids and their synthetic nitro‐derivatives have been investigated by polarography and electron paramagnetic resonance (EPR) spectroscopy under electrochemical reduction in acetonitrile, dimethylformamide (DMF), dimethylsulfoxide (DMSO) or 1,2‐dimethoxyethane. All the compounds studied are reduced in the first stage by one‐electron transfer, apart from flavanone, which accepts two electrons simultaneously. However, the primary radical anions were detected by EPR spectroscopy only for 4′‐nitroflavone. It was shown that radical anions of other flavonoids quickly dimerized. The analysis of the temperature dependence of the hyperfine interaction constants and broadening of lines in EPR spectra of 4′‐nitroflavone radical anions has shown that the distribution of spin density is due to both the change of polarity of the medium and rotation of the nitrophenyl moiety. The assignment of hyperfine structure constants for the 4′‐nitroflavone radical anion was confirmed by density functional theory (DFT) calculations. Copyright © 2011 John Wiley & Sons, Ltd.     

The application of a piezoelectric scanning Fabry-Perot Interferometer to the study of atomic line sources—III: Use of the channeled spectra produced with a continuum source for studies of the absorption line-width for calcium atoms in flames

An instrumental arrangement has been developed for the interferometric study of the half-width of atomic lines in absorption using a spectral continuum source. The variation of observed half-width of the calcium absorption line at 422·67 nm with calcium concentration has been examined in air-acetylene and nitrous oxide-acetylene flames supported as cylindrical flames with and without flame shielding and at long path burners. Extrapolation of the curves obtained to zero added calcium concentration in the flame may allow for correction for self-absorption and flame characteristics and calculation of collisional broadening half-widths and damping constants (a-parameters).     

High-resolution infrared spectrum of the nu1 Ba nd of eta5-C5H5NiNO

Gas-phase rotational constants and distortion constants have been determined for the nu1 (v=1) excited vibrational state of cyclopentadienylnickel nitrosyl (C5H5NiNO) using a high-resolution Fourier transform spectrometer system at Kitt Peak, Arizona. The rotationally resolved lines have been measured for the C-H symmetric stretch vibration (nu1=3110 cm(-1)). In the present analysis, over 150 lines have been assigned and fitted using a rigid-rotor Hamiltonian with centrifugal distortion. The vibrational band center, excited-state rotational constants, and distortion constants derived from the measured spectrum for this prolate symmetric-top molecule are nuo=3110.4129(4) cm(-1), A'=0.14328(8) cm(-1), B'=C'=0.041285(1) cm(-1), DJ'=0.078(1) kHz, DJK'=2.23(4) kHz, and DK'=-2.63(2) kHz, respectively. Several different combination differences, with a common upper state, were calculated for different K stacks for the observed spectra, and the consistency of the lower state rotational constants obtained provided further support for the current assignment. The ground-state rotational constant (B') derived from this combination differences analysis agrees with the previously obtained Fourier transform microwave value to within 0.15%. However, ground-state rotational constants, A' and B', have been fixed in the present analysis to avoid correlation effects and to get more accurate results. The new measured parameters are compared with the previously obtained results from Fourier transform microwave and infrared spectroscopy measurements. The C-H vibration stretching frequency and rotational constants were calculated using density functional theory calculations, and these were quite helpful in resolving ambiguities in the fitting procedure and for initial assignments of measured lines.     

On the use of the Hα spectral line to determine the electron density in a microwave (2.45 GHz) plasma torch at atmospheric pressure

The electron density of an argon microwave (2.45 GHz) plasma flame generated at atmospheric pressure has been determined by using the Stark broadening of the experimentally measured H_α line emitted by the discharge. The H_β line was not observable under the experimental conditions of this discharge. Two methods have been employed to obtain the electron density from the Stark broadening of the H_α line. The first used the Gigosos–Cardeñoso computational model that considers the strong broadening of the H_α line by ionic dynamics. Alternatively, a second method based on a calibration of Stark broadenings of H_α and H_β lines offered a simpler way to obtain the electron density.     

Line frequency shift measurements by diode-laser spectroscopy for CH(3)D-Xe

The pressure-induced Xe shifting and broadening coefficients for five lines of 12CH(3)D in the nu(3) band near 7.5 microm have been measured using a tunable diode-laser spectrometer. The frequency shift was determined from the simultaneous record of the Xe-broadened line and the same line of pure CH(3)D at low pressure. Comparisons are made with the results of theoretical calculations based on a semiclassical model involving the atom-atom Lennard-Jones (LJ) potential.     

Temperature changes in solvent extractions of cadmium oxinate

The extraction of 10^-5.1M cadmium ion from aqueous solution into chloroform containing oxine has been investigated and the effects caused by changing the temperature were studied. Values of equilibrium constants for all reactions participating in the extraction have been obtained as a function of temperature. Plots of the logarithms of the constants vs. the reciprocal of the absolute temperature gave straight lines. Thermodynamic functions for all reactions involved have been calculated.     

Experimental determination of the Stark widths of Pb I spectral lines in a laser-induced plasma

Stark widths of 34 spectral lines of Pb I have been measured in a Laser-Induced-Plasma (LIP). The optical emission spectroscopy from a LIP generated by a 10 640 Å radiation, with an irradiance of 1.4 × 10¹⁰ W cm^− 2 on a Sn–Pb target in an atmosphere of argon was analyzed between 1900 and 7000 Å. The Local Thermodynamic Equilibrium (LTE) conditions and plasma homogeneity have been checked. The 34 spectral lines measured in this paper correspond to the transitions n(n = 7, 8)s→6p², n(n = 6, 7)d→6p². The population levels distribution and the corresponding temperatures were obtained using Boltzmann plots. The plasma electron densities were determined using well-known Stark broadening parameters of spectral lines. Special attention was dedicated to the possible self-absorption of the different transitions. Stark broadening parameters of the spectral lines were measured at 2.5 µs after each laser light pulse, where the electron temperature was close to 11 200 K and the electron density to 10¹⁶ cm^− 3. The experimental results obtained have been compared with the experimental values given by other authors.     

High-resolution absorption cross sections of formaldehyde in the 30,285-32,890 cm(-1) (304-330 nm) spectral region

Absolute room temperature (294 ± 2 K) absorption cross sections for the ?(1)A(2)-X?(1)A(1) electronic transition of formaldehyde have been measured over the spectral range 30,285-32,890 cm(-1) (304-330 nm) using ultraviolet (UV) laser absorption spectroscopy. Accurate high-resolution absorption cross sections are essential for atmospheric monitoring and understanding the photochemistry of this important atmospheric compound. Absorption cross sections were obtained at an instrumental resolution better than 0.09 cm(-1), which is slightly broader than the Doppler width of a rotational line of formaldehyde at 300 K (～0.07 cm(-1)) and so we were able to resolve all but the most closely spaced lines. Comparisons with previous data as well as with computer simulations have been made. Pressure broadening was studied for the collision partners He, O(2), N(2), and H(2)O and the resulting broadening parameters have been measured and increase with the strength of intermolecular interaction between formaldehyde and the collision partner. The pressure broadening coefficient for H(2)O is an order of magnitude larger than the coefficients for O(2) and N(2) and will contribute significantly to spectral line broadening in the lower atmosphere. Spectral data are made available as Supporting Information.     

Interferometric measurements of spectral line widths emitted by an inductively coupled plasma

Line widths of fifteen spectral lines of ten elements introduced into an inductively coupled plasma (ICP) have been measured with a Fabry-Pcrot interferometer. Instrumental broadening is estimated by measuring the line widths emitted by hollow-cathode lamps and assuming their actual profiles as purely Gaussian with Doppler widths at 400 K. For correction of the experimental widths of lines emitted by the ICP, actual profiles of the lines are assumed to be purely Gaussian as a first approximation. The calculated actual widths range from 0.0015 to 0.0051 nm. Values of the a-paramctcr of the Voigt profile are estimated by assuming the Doppler temperature of the plasma to be 5000 K. Most of the lines emitted by the ICP have a-values in a range between 0.2 and 0.7. The fact reported previously that ICP lines suffer from less collisional broadening than lines excited in flames is supported.     

Basicity comparison for di-substituted 4-nitropyridine derivatives in polar non-aqueous media

Acid dissociation, as well as cationic homoconjugation equilibria have been studied potentiometrically in systems involving four di-substituted 4-nitropyridines and conjugate cationic acids in the polar non-aqueous solvents - aprotic protophobic acetonitrile (AN) and propylene carbonate (PC), the amphiprotic methanol (MeOH), and in the aprotic protophilic dimethyl sulfoxide (DMSO). The influence of solvent effect on the obtained acidity constants has been discussed. The acidity constants (expressed as pK_a values) were compared with those previously determined in another polar protophobic aprotic solvent - acetone (AC), and obtained for the unsubstituted pyridine (Py). A comparison of the acid dissociation constants determined in all media studied has proved that the strength of the cationic acids increases on going from acetonitrile through propylene carbonate, acetone, and methanol to dimethyl sulfoxide. Furthermore, the values of acidity constants in the non-aqueous media have shown that in all the solvents studied they change according to the substituent effects. It has been also found that substituted 4-nitropyridine derivatives studied exhibit no tendency towards cationic homoconjugation in acetonitrile, propylene carbonate, and methanol and dimethyl sulfoxide. Moreover, it has been demonstrated that the acid dissociation constants determined by potentiometric titration method in all the solutions investigated correlate well with the calculated energy parameters of the protonation reactions in the gaseous phase.     

Non-cytotoxic, bifunctional EuIII and TbIII luminescent macrocyclic complexes for luminescence resonant energy-transfer experiments

A new macrocyclic ligand, L3, has been synthesised, based on the cyclen framework grafted with three phenacyl light-harvesting groups and a C5-alkyl chain bearing a carboxylic acid function as a potential linker for biological material. Acidity constants are determined by spectrophotometric titrations, as well as conditional stability constants for the resulting 1:1 complexes with trivalent lanthanide ions. The complexes have stabilities comparable to 1,4,7,10-tetrakis(carbamoylmethyl)-1,4,7,10-tetraazacyclododecane (dtma) complexes, with pLn approximately 12-13. Photophysical properties of the ligand and of the EuL3 and TbL3 complexes have been determined for both microcrystalline samples and solutions in water and acetonitrile. They point to the metal ion being present in an environment with axial symmetry derived from the C4 point group. The hydration number determined for TbL3 decreases with increasing pH value and becomes fractional at pH 7.5, which points to an equilibrium between two differently solvated species and probably to the participation of the deprotonated carboxylic acid chain in the complexation. The quantum yields in water (1.9% for EuIII, 3.4% for TbIII) are smaller than those for complexes with the symmetrically substituted parent macrocycle, but efficient luminescence resonant energy transfer (LRET) was observed when Cy5 dye was added to the solutions. Finally, the influence of the TbL3 complex on cell viability is tested on both malignant (5D10 mouse hybridoma, Jurkat human T leukaemia, MCF-7 human breast carcinoma) and non-malignant (Hacat human keratinocyte) cell lines. Cell viability after 24 h incubation at 37 degrees C with 500 microM TbL3 was >90% for all cell lines, except Jurkat (>70%). All of these properties make LnL3 complexes interesting potential probes for bioanalyses.     

The use of14C,59Fe and65Ni radionuclides for the study of solvent effects on the extraction equilibria with n-caprylic acid

The distribution of n-caprylic acid between an aqueous sodium sulphate solution and several organic diluents of various properties has been investigated, using¹⁴C-labelled n-caprylic acid. The distribution coefficients of the monomeric capyrlic acid and its dimerization constants in the organic phase were determined. The extraction of Fe(III) and Ni(II) with n-caprylic acid solutions in various diluents was studied using the AKUFVE solvent extraction equipment. The composition of the extracted compound of Fe(III) has been determined and the extraction constants for all the studied systems have been calculated. For the extraction of Ni(II) the constants of the extraction of nickel caprylate monomers and its dimerization constants in the organic phase have been calculated.     

Ion—molecular charge transfer as studied by the method of optically detected ESR of radical pairs

Effects of ion—molecular charge transfer upon optically detected (OD) ESR spectra of radical pairs have been studied experimentally and theoretically. Theoretical analysis has shown that under certain conditions (often realized in experiments) OD ESR spectra are analogous to standard ESR ones. Broadening and collapse of the hyperfine structure (exchange broadening) have been observed experimentally depending on the concentration of neutral acceptors. Ion—molecular charge transfer rate constants have been calculated for some radical-anions from the experimental data.     

Dependence of nuclear quadrupole double resonance spectra on the level of the saturating radio-frequency field

The dependence of the intensity of nuclear quadrupole double resonance (NQDR) lines on the level of the saturating rf field and the nature of its absorption has been studied. It has been shown that the intensity of the solid-state doublets depends on the square of the amplitude of the saturating field. Pure solid-state doublets have been recorded for the first time for amino groups in eight compounds. Picolinamide, nicotinamide, acetamide, and trichloroacetamide comprise a group of compounds with similar values for the quadrupole coupling constants and the asymmetry parameters. Urosulfan, guanidine chloride, urea, and thiourea make up another group. The interproton distances in the amino groups have been determined in all the compounds on the basis of the multiplet structure of the NQDR lines.Translated from Teoreticheskaya i Eksperimental'naya Khimiya, Vol. 21, No. 2, pp. 237–240, March–April, 1985.We thank A. I. Stetsenko for supplying the compounds for the investigation.     

二价钇配位化合物的ESCA的表征

本文用钇的3P_(1/2)和3P(3/2)的间距及3P能级的半高宽(FWHM)的变化以及￥4s能级的多重分裂确定了新合成的有机金属化合物的价态。在铝靶上,利用轫致辐射诱导的俄歇谱,对高动能的YL_3M_(45)M_(45)峰(大约1737eV)进行了研究,进一步验证了钇的价态。这与X射线衍射的结果相互补充。     

Calibration Measurements in laser-induced breakdown spectroscopy using nanosecond and picosecond lasers

The influence of laser pulse duration on laser-induced breakdown spectroscopy (LIBS) calibration curves is investigated in the present work. Two Nd:YAG lasers providing pulses of 35 ps and 5 ns, respectively, both operating at 1064 nm, have been used to create plasmas on aluminium, manganese, iron, and silicon targets and on prepared stoichiometric samples of these metals in a matrix. The time-resolved, space-averaged plasma temperatures have been deduced using Boltzmann plots, while the electron number density has been determined from the broadening of spectral lines. The effect of laser pulse duration on the plasma characteristics is discussed, and comparisons are made with previously reported data measured under similar experimental conditions. The optimum experimental conditions (i.e., time delay, gate width, laser energy) have been determined for reliable use of LIBS for quantitative analysis for both pulse durations. For each of the metals of interest, calibration curves have been constructed for concentrations ranging up to 2%.     

ESR.-Spektrum von Diphenylpicrylhydrazyl (DPPH)

The ESR. sprectra of DPPH in mixed organic solvents have been measured with a K-band superheterodyne spectrometer and self-locking magnetometer with high precision. Approximately 150 lines have been resolved in the spectra. Both the zero and first order derivative spectra were analyzed by a line shape analysis program for determination of the coupling constants. The smallest coupling constant was found to be 377 ± 5 mG, all other coupling parameter are multiples of this constant. A set of most probable coupling constants is given. The two nitrogen coupling constants are found to be equal within experimental error, and there exist several rotational relations and several possible assignments.     

Determination of optical cross-sections for some Na and Li lines with a shock tube

The optical cross-section for collisional broadening of the lines NaI 589.0 nm, LiI 670.7 nm and LiI 610.3 nm by argon was determined by simultaneous measurement of the total absorption and the density of active atoms that were thermally excited in a shock tube. It was found that the method is suitable for both resonance lines and lines originating from transitions between higher excited levels.