Measured Line Intensities Research Articles

Detection of 5-fluorouracil surface contamination in near real time.

Contamination of workplace surfaces by antineoplastic drugs presents an exposure risk for healthcare workers. Traditional instrumental methods to detect contamination such as gas chromatography-mass spectrometry (GC-MS) or liquid chromatography-tandem mass spectrometry (LC-MS/MS) are sensitive and accurate but expensive and incapable of producing results in real time. This limits their utility in preventing worker exposure. We are currently developing monitors based on lateral flow immunoassay that can detect drug contamination in near real time. In this report, we describe the laboratory performance of a 5-fluorouracil (5-FU) monitor. The monitor was evaluated by spiking ceramic, vinyl, composite, stainless steel, and glass surfaces of 100 cm(2) area with 5-FU masses of 0, 5, 10, 25, 50, and 100 ng. The surface was sampled with a wetted cotton swab, the swab was extracted with buffer, and the resulting solution was applied to a lateral flow monitor. Two ways of evaluating the response of these monitors were used: an electronic method where a lateral flow reader was used for measuring line intensities, and a visual method where the intensity of the test line was visually compared to the control line. The 5-FU monitor is capable of detecting 10 ng/100 cm(2) (0.1 ng/cm(2)) using the electronic reader and 25 ng/100 cm(2) (0.25 ng/cm(2)) using the visual comparison method for the surfaces studied. The response of the monitors was compared to LC-MS/MS results for the same samples for validation and there was good correlation of the two methods but some differences in absolute response, especially at higher spiking levels for the surface samples.

Excited State Distributions of Hydrogen Atoms in the Microwave Discharge Hydrogen Plasma and the Effect of Electron Energy Probabilistic Function

To understand the essentiality of the electron energy distribution function in a low-pressure discharge plasma, an experimental study is carried out on the diagnostics of microwave discharge hydrogen plasma with its discharge pressure ~1 torr in a cylindrical quartz tube. The electron kinetic temperature and density are measured by a Langmuir double probe. Number densities of electronically excited states of hydrogen atoms are experimentally examined by an optical emission spectroscopic (OES) measurement of line intensities of the Balmer series. The rotational and vibrational temperatures are observed for the Fulcher-α band spectrum of hydrogen molecule to understand the approximate value to the neutral gas temperature. The number density of the ground state of hydrogen atom is also experimentally estimated from the actinometry measurement. The electron energy probabilistic function (EEPF) is numerically calculated as a solution to the Boltzmann equation. Number densities of excited hydrogen atoms are calculated with the collisional-radiative (CR) model with experimentally measured data as input parameters. It is found that the population densities of excited states of hydrogen atoms become about one order or much larger than those determined by OES measurement if we assume Maxwellian EEPF. The CR model with the EEPF as a solution to the Boltzmann equation theoretically reproduce the experimentally measured values very well.

NON-EQUILIBRIUM MODELING OF THE FE XVII 3C/3D LINE RATIO IN AN INTENSE X-RAY FREE-ELECTRON LASER EXCITED PLASMA

Recent measurements using an X-ray Free Electron Laser (XFEL) and an Electron Beam Ion Trap at the Linac Coherent Light Source facility highlighted large discrepancies between the observed and theoretical values for the Fe xvii 3C/3D line intensity ratio. This result raised the question of whether the theoretical oscillator strengths may be significantly in error, due to insufficiencies in the atomic structure calculations. We present time-dependent spectral modeling of this experiment and show that non-equilibrium effects can dramatically reduce the predicted 3C/3D line intensity ratio, compared with that obtained by simply taking the ratio of oscillator strengths. Once these non-equilibrium effects are accounted for, the measured line intensity ratio can be used to determine a revised value for the 3C/3D oscillator strength ratio, giving a range from 3.0 to 3.5. We also provide a framework to narrow this range further, if more precise information about the pulse parameters can be determined. We discuss the implications of the new results for the use of Fe xvii spectral features as astrophysical diagnostics and investigate the importance of time-dependent effects in interpreting XFEL-excited plasmas.

The absorption spectrum of water vapor in the 1.25 μm atmospheric window (7911–8337 cm−1)

The absorption spectrum of water vapor in “natural” isotopic abundance has been recorded at room temperature by high sensitivity Continuous Wave Cavity Ring Down Spectroscopy (CW-CRDS) between 7911 and 8337cm−1. The investigated region covers most of the 1.25µm transparency window of importance for atmospheric applications. The recordings were performed with sensitivity on the order of αmin~2×10–11cm−1, more than two orders of magnitude better than previous investigations by Fourier Transform Spectroscopy (FTS). Measured line intensities cover a range of seven orders of magnitude (3×10–30–2×10–23cm/molecule at room temperature). The experimental line list provided as Supplementary Material includes more than 5000 transitions. As a result of the achieved sensitivity, more than 1150 lines of the experimental list were identified as being due to ammonia present as an impurity at the 5ppm concentration level in the water sample. Although incomplete, the obtained ammonia line list seems to be the first one in the region. More than 3193 water lines were assigned to 3560 transitions of five water isotopologues (H216O, H218O, H217O, HD16O and HD18O). The assignments were performed using known experimental energy levels and calculated spectra based on variational calculations by Schwenke and Partridge. The obtained results are compared to the most relevant previous studies by Fourier Transform Spectroscopy in the region and to the exhaustive review of rovibrational line positions and levels performed recently by an IUPAC sponsored task group. Two-hundred and sixty-six levels are newly determined and 46 are corrected by more than 0.015cm−1 compared to those recommended by the water IUPAC task group. The overall agreement between variational and measured intensities is satisfactory.A complete empirical list of 4473 transitions incorporating all the experimental information at disposal was constructed for water in the studied region. The intensity cut-off was fixed to 1×10–29cm/molecule at 296K. A detailed comparison with the line list as provided by the HITRAN database illustrates the advantages of the new list.

A hybrid calibration-free/artificial neural networks approach to the quantitative analysis of LIBS spectra

A ‘hybrid’ method is proposed for the quantitative analysis of materials by LIBS, combining the precision of the calibration-free LIBS (CF-LIBS) algorithm with the quickness of artificial neural networks. The method allows the precise determination of the samples’ composition even in the presence of relatively large laser fluctuations and matrix effects. To show the strength and robustness of this approach, a number of synthetic LIBS spectra of Cu–Ni binary alloys with different composition were computer-simulated, in correspondence of different plasma temperatures, electron number densities and ablated mass. The CF-LIBS/ANN approach here proposed demonstrated to be capable, after appropriate training, of ‘learning’ the basic physical relations between the experimentally measured line intensities and the plasma parameters. Because of that the composition of the sample can be correctly determined, as in CF-LIBS measurements, but in a much shorter time.

Vacuum ultraviolet spectroscopy in detached plasmas with impurity gas seeding in LHD

We have carried out vacuum ultraviolet (VUV) spectroscopy of impurity ions in detached plasmas with impurity gas seeding in the Large Helical Device (LHD). In neon (Ne) gas seeding experiments, temporal evolutions of VUV spectral lines from Ne IV–VIII were recorded by a grazing incidence spectrometer. In addition, spatial profiles of fully ionized Ne density were measured by charge exchange spectroscopy. An electron temperature range where each ion emits is inferred based on the comparisons of the measured line intensity ratios with the calculations using collisional-radiative models.

Ionization Mechanism and Chemical Composition of an Argon DC Discharge with Water Cathode

This paper reports the results of the experimental study and chemical composition modeling for a DC argon discharge burning above water cathode in the pressure range of 0.1–1 bar and at discharge current of 40 mA. The gas temperature, reduced electric field strength, and emission intensities of some argon lines were obtained. On the base of these data, the modeling chemical composition of plasma was carried out. At modeling, the combined solution of Boltzmann equation for electrons, equations of vibrational kinetics for ground states of N2, O2, H2O and NO molecules, equations of chemical kinetics and plasma conductivity equation was used. The calculations agree well with the measured line intensities. It was shown that discharge burns in diffusion mode, at which the stepwise ionization rate of four lower excited states of argon is equal to the rate of charges diffusion losses.

Line shapes, positions and intensities of water transitions near 1.28 μm

We present measurements of approximately 70 isolated, self-broadened, water vapor lines which are assigned to the (1,0,1)–(0,0,0), (0,0,2)–(0,0,0), (1,2,0)–(0,0,0), and (2,0,0)–(0,0,0) vibrational bands and which occur in the transparency window region from 7710cm−1 to 7920cm−1. We acquired absorption spectra on room-temperature, water samples over the pressure range 150–800Pa with the frequency-stabilized cavity ring-down spectroscopy technique. In order to optimize measurement accuracy, we integrated mK-level temperature control and SI-traceable pressure measurements into our cavity ring-down spectroscopy measurements. This technique yielded relative uncertainties of 0.04% and 0.20% in sample density and measured line intensity, respectively. We also referenced our spectrum frequency axes to a Cs clock, which provided vacuum line positions with a combined standard uncertainty of 3MHz. Comparison of our measured intensities, positions and self-broadening parameters with literature values reveals that the present work substantially reduces uncertainty in these line parameters. For the (1,0,1)–(0,0,0) vibrational band, the measured line intensities agree at the 1%-level with published ab initio calculations. Our spectra exhibited signal-to-noise ratios up to ≈20,000:1 to enable stringent tests of theoretical line profiles through multispectrum least-squares data analysis. We show that the partially correlated, quadratic-speed-dependent Nelkin–Ghatak profile gives a quality of fit that is commensurate with the high spectrum signal-to-noise ratio, and unlike most other profiles considered here, reproduces the measured line shapes without systematic residuals over the entire pressure range. Our results confirm that mechanisms of (1) collisional narrowing, (2) speed-dependent effects and (3) partial correlation between velocity-changing and dephasing collisions, contribute to the self-broadened line shape of isolated water vapor transitions.

Self-broadening coefficients and improved line intensities for the ν7 band of ethylene near [formula omitted], and impact on ethylene retrievals from Jungfraujoch solar spectra

Relying on high-resolution Fourier transform infrared (FTIR) spectra, the present work involved extensive measurements of individual line intensities and self-broadening coefficients for the ν7 band of 12C2H4. The measured self-broadening coefficients exhibit a dependence on both J and Ka. Compared to the corresponding information available in the latest edition of the HITRAN spectroscopic database, the measured line intensities were found to be higher by about 10% for high J lines in the P branch and lower by about 5% for high J lines of the R branch, varying between these two limits roughly linearly with the line positions. The impact of the presently measured line intensities on retrievals of atmospheric ethylene in the 949.0–952.0cm−1 microwindow was evaluated using a subset of ground-based high-resolution FTIR solar spectra recorded at the Jungfraujoch station. The use of HITRAN 2012 with line intensities modified to match the present measurements led to a systematic reduction of the measured total columns of ethylene by −4.1±0.1%.

Surface loss probability of atomic hydrogen for different electrode cover materials investigated in H2-Ar low-pressure plasmas

In an inductively coupled H2-Ar plasma at a total pressure of 1.5 Pa, the influence of the electrode cover material on selected line intensities of H, H2, and Ar are determined by optical emission spectroscopy and actinometry for the electrode cover materials stainless steel, copper, tungsten, Macor®, and aluminum. Hydrogen dissociation degrees for the considered conditions are determined experimentally from the measured emission intensity ratios. The surface loss probability βH of atomic hydrogen is correlated with the measured line intensities, and βH values are determined for the considered materials. Without the knowledge of the atomic hydrogen temperature, βH cannot be determined exactly. However, ratios of βH values for different surface materials are in first order approximation independent of the atomic hydrogen temperature. Our results show that βH of copper is equal to the value of stainless steel, βH of Macor® and tungsten is about 2 times smaller and βH of aluminum about 5 times smaller compared with stainless steel. The latter ratio is in reasonable agreement with literature. The influence of the atomic hydrogen temperature TH on the absolute value is thoroughly discussed. For our assumption of TH = 600 K, we determine a βH for stainless steel of 0.39 ± 0.13.

On the performance of laser-induced breakdown spectroscopy for direct determination of trace metals in lubricating oils

Laser-induced breakdown spectroscopy (LIBS) provides a technique to directly determine metals in viscous liquids and especially in lubricating oils. A specific laser ablation configuration of a thin layer of oil applied on the surface of a pure aluminum target was used to evaluate the analytical figures of merit of LIBS for elemental analysis of lubricating oils. Among the analyzed oils, there were a certified 75cSt blank mineral oil, 8 virgin lubricating oils (synthetic, semi-synthetic, or mineral and of 2 different manufacturers), 5 used oils (corresponding to 5 among the 8 virgin oils), and a cooking oil. The certified blank oil and 4 virgin lubricating oils were spiked with metallo-organic standards to obtain laboratory reference samples with different oil matrix. We first established calibration curves for 3 elements, Fe, Cr, Ni, with the 5 sets of laboratory reference samples in order to evaluate the matrix effect by the comparison among the different oils. Our results show that generalized calibration curves can be built for the 3 analyzed elements by merging the measured line intensities of the 5 sets of spiked oil samples. Such merged calibration curves with good correlation of the merged data are only possible if no significant matrix effect affects the measurements of the different oils. In the second step, we spiked the remaining 4 virgin oils and the cooking oils with Fe, Cr and Ni. The accuracy and the precision of the concentration determination in these prepared oils were then evaluated using the generalized calibration curves. The concentrations of metallic elements in the 5 used lubricating oils were finally determined.

Determination of the Electron Temperature of Atmospheric Pressure Argon Plasmas by Absolute Line Intensities and a Collisional Radiative Model

The electron temperature in atmospheric argon plasmas created by a DBD jet is determined using a combination of Absolute Line Intensity (ALI) measurements and a collisional radiative model (CRM). The ALI measurements have been performed to determine the densities of the states in the 4p level. In addition, the ground state density is taken into account, which is found via the pressure and the gas temperature. The density ratio of the ground state and 4p state gives a value of the excitation temperature, which by means of the CRM is transformed into the electron temperature. With this method, the electron temperature in the active zone of a pure argon plasma is found to be 1.27 eV which is significantly higher than the experimental value reported by others. An error analysis shows that the relative error in the electron temperature obtained in this way is about 5%. In the afterglow, the temperature decreases gradually to about 0.88 eV. The addition of 2% O2 leads to a decrease in electron temperature of about 5%.

A modified Fowler–Milne method for monochromatic image analysis in multi-element arc plasma welding

The monochromatic images of 794.8nm Ar I and 487.98nm Ar II spectrums are obtained by high speed camera, and these images are normalized with respect to their relative maximum emission coefficient in a pure argon (single element) arc. The relative maximum emission coefficient of 487.98nm Ar II is calculated based on Olsen-Richter diagram. Unlike other spectroscopic methods, the presented method does not require spectra scan or the maximum emission coefficient of non-argon elements. This technique is applied to the measurement of radial profile of temperature and gas composition of argon–helium arc plasma in gas tungsten arc welding (GTAW), significant demixing occurs in the argon–helium arc plasma. Helium concentration in arc plasma is higher than that in original gas mixture, and it decreases as the point moves away from the axis along radial direction and increases as the point gets closer to the cathode. The calculated arc temperature and gas composition are compared with the data obtained using conventional method where a spectrometer is used for spectral line intensity measurement and two-line relative intensity method for calculation. Very good agreements have been observed. That means, the developed technique measures arc temperature and gas composition as accurate as the conventional spectroscopic methods. With the usage of a high speed camera, the developed technique enables measurement of arc temperature and gas composition distribution in a dynamic arc such as arc ignition, pulsing arc.

Intracavity Laser Absorption Spectroscopy of 13C16O2 near 734 nm

We report the first intensity measurements for the very weak 20052-00001 band of the 2ν1+5ν3 triad of 13C16O2 near 734nm by high sensitivity Intracavity Laser Absorption Spectroscopy. A noise equivalent absorption αmin∼2×10−10cm−1 was achieved with an absorption pathlength equivalent to 50.3km. The derived intensity values (on the order of 10−28cm/molecule) are found in good agreement with recent ab initio calculations. The dominant term of the effective dipole moment of the 2ν1+5ν3 triad was obtained from a fit of the measured line intensity values and used to generate the line list of the 2ν1+5ν3 triad of 13C16O2 and 12C16O2.

Adaptive real-time dual-comb spectroscopy

The spectrum of a laser frequency comb consists of several hundred thousand equally spaced lines over a broad spectral bandwidth. Such frequency combs have revolutionized optical frequency metrology and they now hold much promise for significant advances in a growing number of applications including molecular spectroscopy. Despite an intriguing potential for the measurement of molecular spectra spanning tens of nanometres within tens of microseconds at Doppler-limited resolution, the development of dual-comb spectroscopy is hindered by the demanding stability requirements of the laser combs. Here we overcome this difficulty and experimentally demonstrate a concept of real-time dual-comb spectroscopy, which compensates for laser instabilities by electronic signal processing. It only uses free-running mode-locked lasers without any phase-lock electronics. We record spectra spanning the full bandwidth of near-infrared fibre lasers with Doppler-limited line profiles highly suitable for measurements of concentrations or line intensities. Our new technique of adaptive dual-comb spectroscopy offers a powerful transdisciplinary instrument for analytical sciences.

High sensitivity Cavity Ring Down spectroscopy of 18O enriched carbon dioxide between 5850 and 7000 cm−1: Part III–Analysis and theoretical modeling of the 12C17O2, 16O12C17O, 17O12C18O, 16O13C17O and 17O13C18O spectra

More than 19,700 transitions belonging to 11 isotopologues of carbon dioxide have been assigned in the room temperature absorption spectrum of highly 18O enriched carbon dioxide recorded by very high sensitivity CW-Cavity Ring Down spectroscopy between 5851 and 6990cm−1 (1.71–1.43μm). This third and last report is devoted to the analysis of the bands of five 17O containing isotopologues present at very low concentration in the studied spectra: 16O12C17O, 17O12C18O, 16O13C17O, 17O13C18O and 12C17O2 (627, 728, 637, 738 and 727 in short hand notation). On the basis of the predictions of effective Hamiltonian models, a total of 1759, 1786, 335, 273 and 551 transitions belonging to 24, 24, 5, 4 and 7 bands were rovibrationally assigned for 627, 728, 637, 738 and 727, respectively. For comparison, only five bands were previously measured in the region for the 728 species. All the identified bands belong to the ΔP=8 and 9 series of transitions, where P=2V1+V2+3V3 is the polyad number (Vi are vibrational quantum numbers). The band-by-band analysis has allowed deriving accurate spectroscopic parameters of 61 bands from a fit of the measured line positions. Two interpolyad resonance perturbations were identified.Using the newly measured line positions and those collected from the literature, the global modeling of the line positions within the effective Hamiltonian approach was performed and a new set of Hamiltonian parameters was obtained for the 17O12C18O, 16O13C17O and 17O13C18O isotopologues. For the five studied isotopologues, the effective dipole moment parameters of the ΔP=8 and 9 series were derived from a global fit of the measured line intensities. The obtained results will be used for the improvement of the quality of the line positions and intensities in the most currently used spectroscopic databases of carbon dioxide.

Atomic emission spectroscopy method for mixing studies in high power thermal plasmas

Atomic emission spectrometry was used to measure the distribution of concentration ratios and temperature in thermal plasmas produced by high power torches for process engineering. The spectroscopic method is based on absolute line intensity measurement and Abel inversion. Assuming local thermal equilibrium, the temperature is deduced from the absolute emission of an argon line and the concentration ratio is deduced from the emission ratio of two lines. Using the two dimensions of the camera for spatial and spectral resolution, fast measurements with high resolution can be done. The method has been tested on a 60kW inductively coupled plasma torch at atmospheric pressure. The results show that the concentration ratios n(O)/n(Ar) and n(H)/n(Ar) can be measured with an accuracy of 25% and that errors due to deviations from LTE are small. Demixing occurs in the induction zone. The application of the method showed that hydrogen diffuses much more than oxygen. The main disadvantage of this method is that, using emission, it does not permit to measure the concentration in the “cold” zones in the center and at the edge of the plasma.

An improved line list for water vapor in the 1.5 µm transparency window by highly sensitive CRDS between 5852 and 6607 cm−1

The absorption spectrum of water vapor in “natural” isotopic abundance has been recorded by high sensitivity Continuous Wave Cavity Ring Down Spectroscopy (CW-CRDS) between 5852 and 6607cm−1. The investigated region covers the 1.5µm transparency window of major importance for atmospheric applications. The achieved sensitivity of the recordings varies from αmin ∼2×10−11 to 2×10−10cm−1 and allows for a significant amount of new or more accurate observations compared to previous studies. Measured line intensities cover a range of six orders of magnitude (2×10−30−2×10−24cm/molecule at room temperature). The vibration–rotation assignments were performed using known experimental energy levels and calculated spectra based on variational calculations by Schwenke and Partridge.Five thousand seven hundred and twenty seven lines were assigned to 6379 transitions of six water isotopologues (H216O, H218O, H217O, HD16O, HD18O and HD17O). The first detection of lines due to HD17O in “natural” water (relative abundance on the order of 1.1×10−7) illustrates the sensitivity of the recordings. Most of the 1842 newly reported transitions belong to the main isotopologue (1022 transitions) and to the HD16O isotopologue (684 transitions). Sixty-three levels are newly determined and 22 are corrected by more than 0.015cm−1 compared to those recommended by the water IUPAC task group.Overall, a list of 6589 transitions was constructed for the studied region. The present CRDS line list complemented with 210 strong transitions from the literature is believed to be the most complete empirical list of the region. The obtained results are critically compared to recent IUPAC task group compilations. Overall the agreement between variational and measured intensities is very satisfactory. We nevertheless point out a number of important disagreements for some lines of the highly excited bending bands, mainly 4ν2 of H216O.

Measurements of 12C16O2 line parameters in the 8790–8860, 9340–9650 and 11,430–11,505 cm−1 wavenumber regions by means of Fourier transform spectroscopy

Absorption spectra of carbon dioxide, 12C16O2, have been studied in the three wavenumber ranges (8790–8860, 9340–9650 and 11,430–11,505cm−1) of the near infrared region using spectrophotometric complex of V.E. Zuev Institute of Atmospheric Optics based on an Bruker IFS 125 HR and a 30m multipass cell with the White type optical system. The spectra were recorded at spectral resolution of 0.015cm−1, path length of 613.82m and at pressure range from 209 to 400mbar. The multispectrum fittings with the Voigt profile were performed to retrieve the line positions and intensities of eight bands 5001r−00001 (r=3, 4), 2003r−00001 (r=1,2,3) 2113r−01101 (r=1,2) and 00051−00001. The uncertainty of the line position determination is estimated to be about 0.001cm−1. The absolute accuracy of the line intensity measurement is 5% for 5001r−00001 (r=3,4) bands, 3% for 2003r−00001 (r=1,2,3) bands, 10% for 00051−00001 band and 15% for 2113r−01101 (r=1,2) bands. The measured line intensities were used to fit the effective dipole moment parameters of 12C16O2. The fitted parameters reproduce the measured line intensities within their experimental uncertainties. A comparison of measured positions and intensities with those contained in HITRAN, CDSD, AMES-296, and High-T databases is presented and discussed.

Discharge character and optical emission in a laser ablation nanosecond discharge enhanced silicon plasma

Nanosecond discharge enhanced laser-induced breakdown spectroscopy of silicon was investigated. An intense discharge spark was observed with a peak discharge current of 1.63 kA and a peak power of 8.1 MW, and only lasted for ∼51 ns. The discharge stability and the effect of the capacitances on the discharge and optical emission were investigated. A stable discharge process and optical emission were observed. The precision in terms of the relative standard deviation (RSD) of time delay between the laser firing and discharge was 1.7% with a discharge voltage of 9 kV, while the RSD of line intensities from repeatable measurements was typically about 2–3%. The measured line intensities of atomic and ionic states of silicon were used for electron temperature calculation by employing Saha–Boltzmann plots. Electron number density was determined by using the Stark broadening of two silicon atomic lines. Compared to the laser induced plasma, the temperature of the discharge enhanced plasma was increased, while the electron number density in the discharge plasma was roughly the same in the laser ablation nanosecond discharge enhanced Si plasma.