Copper Hollow Cathode Research Articles

Rotational and deperturbation analysis of the (0,0) and (1,0) vibrational bands of the [15.30]1 – X3Σ–(0+) transition of WS

The (0,0) and (1,0) bands of the [15.30]1 – X3Σ–(0+) transition of tungsten sulfide (WS) were recorded at high resolution using intracavity laser spectroscopy integrated with a Fourier-transform spectrometer for detection (ILS-FTS). The target WS molecules were produced in the plasma discharge of a tungsten-lined copper hollow cathode, using a gas mixture of approximately 70 % Ar and 30 % H2, with a trace amount of CS2. The total pressure in the reaction chamber was about 1 torr. Evidence of heterogeneous mass- and J-dependent perturbations was observed in each spectrum for all four abundant isotopologues: 182W32S, 183W32S, 184W32S, and 186W32S. The perturbations were attributed to interactions with the v = 2 and v = 3 vibrational levels of the [14.26]0+ state of WS. A rotational analysis with deperturbation analysis was performed using PGOPHER to determine parameters for both states. A Dunham-like model which constrains parameters to expected mass relationships was used to describe the perturbed states.

Analysis of the (0,0) band of the new [15.3]Ω=3/2 – X2Π3/2 electronic transition of PtF using intracavity laser spectroscopy

A rotational analysis of the electronic transition of PtF occurring at 15,252 cm−1 was recorded and analyzed. This transition is identified as the (0,0) band of the [15.3]Ω=3/2 – X2Π3/2 electronic transition. The PtF molecules were produced in a current regulated RF-pulsed DC discharge operating with 0.80 A applied to a Pt-lined copper hollow cathode in 0.50–1.25 Torr of 1–5% SF6 in an Ar/He sputter gas mixture. The hollow cathode was placed within in the resonator cavity of a tunable DCM dye laser operating over the 14,500–16,500 cm−1 range, and path lengths of 0.2–2.0 km were utilized with the intracavity laser spectroscopy (ILS) method. The data were fit in PGOPHER using a polynomial energy level expression. Molecular constants for the excited state are presented. The nature of the new [15.3]Ω = 3/2 state is discussed.

Microsecond pulsed glow discharge in copper hollow cathode reveals a new approach to ionization and determination of volatile organic compounds

Recently glow discharge (GD) mass spectrometry, which is conventionally used to analyze solid samples, was successfully applied for ionization and the subsequent determination of volatile organic compounds (VOCs). In the present study, the possibility of direct determination of VOCs in ambient air using time-of-flight mass spectrometry with microsecond pulsed discharge in a copper hollow cathode was considered for the first time. The discharge cell of the mass spectrometer was modified for the direct analysis of gaseous samples by the introduction of a quartz capillary into the argon input channel. Various classes of compounds (aromatic and aliphatic hydrocarbons and derivatives of carboxylic acids) were studied. Particular attention was paid to the ionization mechanisms of VOCs. New mechanisms of chemical and electron ionization, resulting in the formation of associate ions with cathode material (copper) – CuM+, were demonstrated and implemented. Alternative mechanisms of organic compounds ionization in GD may be related to Penning process and proton transfer reactions. These processes are mainly responsible for the formation of molecular and protonated molecular ions. The relative contribution of all these mechanisms can be adjusted by operating parameters. In general, an extremely low degree of fragmentation of molecular ions or associates was observed. Due to its isotopic structure (only two isotopes 63Cu and 65Cu with comparable abundances), the use of copper as cathode material additionally increases the reliability of VOC identification in the form of their CuM+ associates. Such association shifts the detected ions to the region of large masses with fewer interferences and noise related to scattered ions.

Identification of two new electronic transitions of TaF using intracavity laser spectroscopy

Several bands in two new electronic transitions of TaF have been recorded in high resolution using intracavity laser absorption spectroscopy (ILS). The (1,0), (0,0), and (0,1) bands of the [16.0]0+ – X3Σ−(0+) transition and the (2,1), (1,0), (0,0), (0,1), and (1,2) bands of the [16.3]1 – X3Σ−(0+) transition were observed. TaF was produced in the plasma discharge of a tantalum-lined copper hollow cathode with Ar [1 torr] as a sputter gas and trace of SF6 as a fluoride source. Trace H2 [1%] also was used as it was found to increase the intensity of the observed transitions. The transitions were analyzed using PGOPHER, and the obtained molecular parameters are presented and compared with a previous work.

Identification of two new excited electronic states of NiCl: Analyses of the (1,0) & (0,0) bands of the [13.5] 2Φ7/2 – [0.16] A2Δ5/2 and (0,0) band of the [13.8] 2Π1/2 – [0.38] X2Π1/2 transitions

The near-infrared spectrum of NiCl has been recorded at high resolution in the 13,200–13,500cm−1 and 13,600–13,750cm−1 regions using Intracavity Laser Spectroscopy (ILS). The NiCl molecules were produced in the plasma discharge of a Ni-lined copper hollow cathode with 0.3–0.6torr of argon as the sputter gas, and a trace amount of CCl4. Several electronic transitions were observed, including three transitions involving two previously unreported excited electronic states. The (0,0) and (1,0) bands of the [13.5]2Φ7/2 – [0.16] A2Δ5/2 transition were observed near 13,318cm−1 and 13,709cm−1, respectively. The (0,0) band of the [13.8]2Π1/2 – [0.38]X2Π1/2 transition was observed near 13,480cm−1. With analysis of these transitions, molecular constants have been obtained for eleven of the twelve predicted NiCl doublets states with term energies less than 16,000cm−1. Comparison of experimentally observed transitions with the theoretical work is presented.

The near-infrared spectrum of NiCl: Analysis of vibrational components of system G and system H between 12,500 cm−1 and 13,750 cm−1

The near-infrared spectrum of nickel chloride, NiCl, has been recorded at high resolution from 12,400–12,600cm−1, 13,200–13,500cm−1, and 13,600–13,750cm−1 using intracavity laser absorption spectroscopy, ILS. The NiCl molecules were produced in the plasma discharge of a nickel-lined, copper hollow cathode with ∼1.8torr of Ar as the sputter gas and a trace amount of CCl4 as the chloride source. Several transitions were observed and analyzed, including the (2,0), (1,0), and (0,1) bands of the [13.0] 2Π3/2–X2Π3/2 transition, System G, and the (1,0) band of the [12.3] 2Σ−–X2Π3/2 transition, System H. The transitions were analyzed using PGOPHER and obtained molecular parameters are reported. A potential energy curve for the [13.0] 2Π3/2 state has been constructed using the vibrational information from the analyzed transitions.

Near-infrared spectrum of ZrF by intracavity laser absorption spectroscopy

The (1,1) band of the CΩ=3/2−X2Δ3/2 transition of ZrF has been recorded at high resolution using intracavity laser absorption spectroscopy. The ZrF molecules were produced using a Zr-lined copper hollow cathode sputter source with a trace amount of SF6 as a fluoride source. Molecular constants from the analysis are presented and compared with previous work.

The effect of self-absorption in hollow cathode lamp on its temperature

It has been shown experimentally that even a small error in the calculation of the temperature inside the hollow-cathode lamp (HCL) and the current applied to the lamp, may cause a tremendous error in determination of the absorption ratio in optical resonance absorption (ORA) method. This effect is intensified nonlinearity for large absorption ratios. If a higher current is applied to a copper hollow cathode lamp, the copper density inside the lamp is increasing rapidly. Due to the cylindrical (axisymmetric) form of the lamp, the density of atoms around the main axis of the lamp becomes greater than that near the internal wall. In this case the auto-absorption (or self-absorption) is occurred and as its result, the emission spectrum produced by copper atoms is locally absorbed before going out from the lamp. This absorption is stronger near the main axis compared with the areas near the wall because of the Gaussian profile of the spectral line. Two different Cu atoms ground state lines with the similar lower state (327.4 nm and 324.7 nm) are used in this work as optical resonance absorption and the absorption coefficient is obtained for three different pressures (0.6, 4.5 and 14 µbar). The best values for copper HCL temperature and for maximum HCL current were found respectively 450 K, and 5mA.

A study and evaluation on a homemade copper hollow cathode discharge laser and designed pulsed power supply parameters

In this work a copper hollow cathode discharge laser was designed and built to utilize copper transitions parameters for laser investigation. A suitable D.C pulse power was constructed particularly to operate this system. The cathode is a free oxygen copper operated in evacuated glass tube and helium in low pressure used as buffer gas. The relation between the pressure and discharge current was investigated and the optimum values obtained at 1.96A for the discharge current and 28 mbar for the pressure of the discharge regime. The spectral lines of the wavelengths 479.72nm, 510.64nm, 558.64nm and 656.61nm were obtained from the spectrum of the emitted intensity have a potential to be laser lines in addition to, possible laser line transitions in the infrared region at wavelengths 782.36 nm. The wavelength of 510.8 nm was selected through a green filter to be oscillated as laser pulses. The maximum output energy of the laser pulse measured by an energy meter is 1.75 m J. The pulse repetition rate measured was 0.670 KHz with pulse duration of 1.4ms. Keywords: hollow cathode, copper ion, pulse power, electrical discharge

Spectroscopic study of hydrogen Balmer line shapes in a hollow cathode glow discharge in NH3 and Ar/NH3, Ar/CH4 and Ar/C2H2 mixtures

The results of Doppler spectroscopy of hydrogen Balmer lines emitted from a stainless steel (SS) and copper (Cu) hollow cathode (HC) low-pressure glow discharge in ammonia, as well as in argon-ammonia, argon-methane and argon-acetylene mixtures are reported. The earlier results of electron beam interactions with NH3, CH4 and C2H2 were used for analysis of Balmer line shapes in HC glow discharge.

Intracavity laser absorption spectroscopy of platinum fluoride, PtF

Abstract Two vibrational bands of an electronic transition of PtF occurring at 11 940 cm −1 and 12 496 cm −1 were recorded and analyzed. These transitions are identified as the (0,0) and (1,0) bands of an [11.9] Ω = 3/2 − X Ω = 3/2 electronic transition. Gas phase PtF was produced in a copper hollow cathode lined with platinum foil using a trace amount of SF 6 , and the spectrum was recorded at Doppler resolution by intracavity laser absorption spectroscopy. This work represents the first published spectroscopic data on PtF. Molecular constants for the ground and excited electronic states are presented.

Doppler spectroscopy of hydrogen Balmer lines in a hollow cathode glow discharge in argon–methane and argon–acetylene mixture

The results of Doppler spectroscopy of hydrogen Balmer lines emitted from a stainless steel (SS) and copper (Cu) hollow cathode (HC) low-pressure glow discharge in argon–methane and argon–acetylene mixtures are reported. The role of dissociative excitation and dissociative ionization and excitation of hydrocarbon molecules in Balmer line shape formation is studied and discussed in relation to earlier electron beam interaction experiments with CH4 and C2H2. Experimental results of excessive Doppler broadening (EDB) of Balmer lines are reported also.

Doppler spectroscopy of hydrogen Balmer lines in a hollow cathode water vapour and argon–water vapour glow discharge

The results of Doppler spectroscopy of hydrogen Balmer lines in a stainless steel (SS) and copper (Cu) hollow cathode (HC) water vapour and argon–water vapour glow discharge are reported. The experimental profiles in water vapour discharge are fitted well by superposing three Gaussian profiles. The half widths of narrow and medium Gaussian are, in energy units, 0.2–0.5 and 3–4 eV for SS HC and 0.14–0.38 and 2.7–3.7 eV for Cu HC which is expected on the basis of earlier electron beam → H2O vapour experiments. The half width of the largest Gaussian in water vapour is 22 eV and 13 eV for SS and Cu HC, respectively. In argon–water vapour discharge three Gaussians are also required to fit experimental profiles. While half widths of narrow and medium Gaussians are similar to those in water vapour, the half width of the largest Gaussian is 37 eV and 28 eV for SS and Cu HC, respectively. The half widths of the largest Gaussian in water vapour and in argon–water vapour mixture indicate the presence of excessive Doppler broadening. The differences in width of the excessively broadened part of the line profiles with SS and Cu HC in water vapour and in argon–water vapour mixture are explained as a consequence of oxide formation at the cathode surface. This study is an attempt to extend and compare our earlier investigations of anomalous Doppler broadening in HC discharge operated with hydrogen isotopes or hydrogen mixtures with inert gases to hydrogen containing inorganic molecules.

Doppler spectroscopy of hydrogen Balmer lines in a hollow cathode glow discharge in ammonia and argon-ammonia mixture

The results of Doppler spectroscopy of hydrogen Balmer lines from a stainless steel (SS) and copper (Cu) hollow cathode (HC) glow discharge in ammonia and argon-ammonia mixture are reported. The experimental profiles in ammonia discharge are fitted well by superposing three Gaussian profiles. The half widths, in energy units, of narrow and medium Gaussians are in the ranges 0.3–0.4eV and 3–4eV, respectively, for both hollow cathodes what is expected on the basis of earlier electron beam→NH3 experiments. The half widths of the largest Gaussian in ammonia are 46 and 55eV for SS and Cu HC, respectively. In argon-ammonia discharge, three Gaussians are also required to fit experimental profiles. While half widths of narrow and medium Gaussians are similar to those in ammonia, the half widths of the largest Gaussians are 35 and 42eV for SS and Cu HC, respectively. The half widths of the largest Gaussians in ammonia and in argon-ammonia mixture indicate the presence of excessive Doppler broadening.

Spectroscopic study of hydrogen rotational, vibrational and translational temperatures in a hollow cathode glow discharge

The optical emission spectroscopy is used for determination of hydrogen molecule rotational Trot, vibrational Tvib, and translational temperature Ttr. The experiment was carried out using copper or titanium hollow cathode discharges operated in pure hydrogen. The rotational temperature of excited electron energy levels is determined from Fulcher-a diagonal bands (d3Πu →a3σ+gelectronic transition, P, Q and R branches), which were later used to derive rovibronic temperature of the hydrogen molecule ground state, which is assumed equal to Ttr. The vibrational temperature Tvib is determined for the same electronic transition (d3Π-u→a3σ+g, with v' = 2,3;δv = 0). For all temperatures the radial temperature distribution is reported.

Rotational and vibrational temperatures of molecular hydrogen in a hollow cathode glow discharge

Optical emission spectroscopy is used for the determination of hydrogen molecule rotational Trot and vibrational Tvib and translational temperature Ttr. The experiment was carried out using copper or titanium hollow cathode discharges operated in pure hydrogen. The rotational temperature of excited electron energy levels is determined from Fulcher-α diagonal bands ( electronic transition, P-, Q- and R-branches), which were later used to derive the rovibronic temperature of the hydrogen molecule ground state, which is assumed equal to Ttr. The vibrational temperature Tvib is determined for the same electronic transition (Q-branch with ν′ = 2,3; Δν = 0). For all temperatures the radial temperature distribution is reported.

Excessive hydrogen and deuterium Balmer lines broadening in a hollow cathode glow discharges

Results of a Doppler spectroscopy study of hydrogen and deuterium Balmer lines in the stainless steel and copper hollow cathode glow discharge, operated in pure hydrogen, deuterium and mixtures of inert gases with hydrogen, are reported. For all gases and gas mixtures plasma observations perpendicular to electric field revealed the excessively large Doppler broadening. By changing mode of glow discharge operation, the Doppler broadened line profiles in helium-hydrogen mixture are recorded parallel to the discharge electric field as well. The excessively broadened part of the Hα line profile is shifted towards blue or red wavelength by changing the direction of electric field vector. The presence of large excessive Balmer lines broadening in pure hydrogen and in its gas mixture with neon as well as shifting of the excessively broadened part of line profile by means of electric field is in contradiction with the resonance transfer model proposed by Mills et al. in several publications, see e.g. [IEEE Trans. Plasma Sci. 31, 338 (2003)].

Study of excitation rates in a hollow cathode discharge

In this work a dc discharge with a copper hollow cathode in argon used for deposition applications is investigated using atomic emission spectroscopy. Typical discharge parameters during our investigation are pressures between 80 and 200 Pa and current densities up to 7 mA cm-2. The radial light intensity profiles of some selected copper and argon lines were measured. An analysis of these profiles gives insigths into the excitation rates of the argon filling gas and the sputtered metal atoms as well as into the radial dimension of the negative glow. The different excitation mechanisms lead to a sharp change of the radial light intensity profiles emitted by many copper spectral lines, which indicates the transition region between the cathode fall and the negative glow. The length of the cathode fall was observed to be very insensitive to all the macroscopic discharge parameters. A nearly constant value was found for the cathode fall length, which corresponds to about 22% of the cathode radius.

Hybrid modeling network for a helium–argon–copper hollow cathode discharge used for laser applications

A hybrid modeling network, consisting of several Monte Carlo and fluid models, is developed for a hollow cathode glow discharge in a mixture of helium and argon, with copper as the cathode material. The species considered in the models are the helium and argon gas atoms, electrons, He+, He2+, Ar+, and Ar2+ ions, He and Ar metastable atoms, fast He and Ar atoms, and sputtered Cu atoms and Cu+ ions. The modeling network is applied to typical laser conditions. The results of the model, presented in this article, include the electric potential distribution, the density profiles of the various plasma species, and the relative contributions of the various production and loss mechanisms for the plasma species. The model gives us more insight into the plasma behavior, and is therefore useful for optimization of the discharge efficiency for laser applications.

High-Resolution Fourier Transform Study of MgCl: The A2Π–X2Σ+ Band System

The A2Π–X2Σ+ emission band system of the MgCl molecule has been studied by means of high-resolution Fourier transform spectroscopy. Excited MgCl molecules were produced by two different techniques: (i) at Orsay, they were created by mixing Mg vapor with a flow of He/Cl2 and excited in a “heated” Schüller-type discharge tube, and (ii) at Waterloo, they were generated by using a copper hollow cathode lamp loaded with MgCl2 powder. Rovibronic analysis of the (0, 0) and (0, 1) bands was performed. Molecular constants were derived in a weighted nonlinear least squares fit, including both the new line positions and the previously published microwave frequencies (M. Bogey, C. Demuynck, and J. L. Destombes, Chem. Phys. Lett.155, 265 (1989); Y. Ohshima and Y. Endo, Chem. Phys. Lett.213, 95 (1993)).