Stainless Steel Hollow Cathode Research Articles

FT-UV emission spectroscopy of the [formula omitted] progression bands of the [formula omitted] system of [formula omitted]C[formula omitted]O[formula omitted]

We report an experimental investigation of the 0−ν′′ progression bands of the First-Negative (B2Σ+−X2Σ+) system of 12C16O+. The ultraviolet wavelength emission spectrum of CO+ was generated using an air-cooled stainless steel hollow-cathode discharge lamp filled with a mixture of CO2 and Ne. The study includes four bands, i.e. 0−0, 0−1, 0−2 and 0−3, observed in emission with a high-resolution Fourier-transform spectrometer in the 38500–46000 cm−1 region. In total, 541 ro-vibronic transitions have been measured with an absolute accuracy of 0.005–0.010 cm−1. The experimental data were analyzed using the PGOPHER program, which resulted in a set of high accuracy molecular constants and ro-vibronic level positions for the X2Σ+, ν=0−3 and B2Σ+, ν=0 levels. The current values of the band origins have been compared with historical data, including the most recent results obtained by Ventura et al. (2020) and the discrepancies pointed out by the authors were explained.

The emission spectroscopy of the [formula omitted] system of the CD radical

The emission spectrum of the 0-0,1-1 and 2-2 bands of the C2Σ+-X2Π system in the CD molecule have been obtained using a stainless steel hollow-cathode lamp with two anodes and filled with a mixture of He buffer gas and CD4. The emission from the discharge was observed with high accuracy dispersive optical spectroscopy using a plane-grating spectrograph and recorded by a photomultiplier tube. In total, 428 transition frequencies belonging to the three bands were precisely measured and rotationally analyzed. The current data were elaborated with the help of precise ro-vibrational and equilibrium ground state parameters reported by Zachwieja et al. (2012) from investigation of the A2Δ-X2Π transition. The spin-rotation interaction constants γv and γD,v of the C2Σ+,v=0,1,2 levels were obtained for the first time. Moreover, the main equilibrium parameters of the third excited state were obtained as follows: Te=31,825.944(12) cm−1, ωe=2078.803(27) cm−1, ωexe=59.558(12) cm−1, Be=7.86810(23) cm−1, αe=0.25315(58) cm−1 and γe=-0.01518(28) cm−1.

A comparative study on electrical characteristics of crystalline AlN thin films deposited by ICP and HCPA-sourced atomic layer deposition

In this work, we aimed to investigate the effects of two different plasma sources on the electrical properties of low-temperature plasma-assisted atomic layer deposited (PA-ALD) AlN thin films. To compare the electrical properties, 50 nm thick AlN films were grown on p-type Si substrates at 200 °C by using an inductively coupled RF-plasma (ICP) and a stainless steel hollow cathode plasma-assisted (HCPA) ALD systems. Al/AlN/p-Si metal-insulator-semiconductor (MIS) capacitor devices were fabricated and capacitance versus voltage (C-V) and current-voltage (I-V) measurements performed to assess the basic important electrical parameters such as dielectric constant, effective charge density, flat-band voltage, breakdown field, and threshold voltage. In addition, structural properties of the films were presented and compared. The results show that although HCPA-ALD deposited AlN thin films has structurally better and has a lower effective charge density (N eff ) value than ICP-ALD deposited AlN films, those films have large leakage current, low dielectric constant, and low breakdown field. This situation was attributed to the involvement of Si atoms into the AlN layers during the HCPA-ALD processing leads to additional current path at AlN/Si interface and might impair the electrical properties.

The emission spectroscopy of the [formula omitted] system of CD

The visible spectrum of CD has been investigated at high resolution between 24,500 and 27,500cm−1 using a high accuracy dispersive optical spectroscopy technique. The CD molecules were produced and excited in a stainless steel hollow-cathode lamp with two anodes and filled with a mixture of He buffer gas and CD4. The emission from the discharge was observed with a plane grating spectrograph and recorded by a photomultiplier tube. The 0–0, 1–0 and 1–1 bands of the B2Σ-–X2Π transition have been registered and measured, while 2–0 and 2–1 absorption bands (Herzberg and Johns, 1969) have been reanalyzed. The current data were elaborated with help of recent X2Π ground state parameters reported by Zachwieja et al. (2012) from investigation of the A2Δ–X2Π transition. This way, the improved spectroscopic constants for the B2Σ- state of CD have been provided as follows: νe=26,050.787(11)cm−1, ωe=1653.019(25)cm−1, ωexe=123.899(12)cm−1, Be=7.08296(32)cm−1, αe=0.30741(84)cm−1, and γe=-0.10727(42)cm−1.

First analysis of the B1Σ+ (υ=1) Rydberg state in the lesser-abundant 12C17O isotopologue on the basis of the 1–υ″ progression of the Ångström band system

So far unobserved in the 12C17O isotopologue, the 1−υ″ progression of the Ångström (B1Σ+–A1Π) band system was recorded under high resolution in the 17,200–22,950cm−1 spectral region as an emission spectrum using high-accuracy dispersive optical spectroscopy. The 12C17O molecules were formed and excited in two steps in a stainless steel hollow-cathode lamp with two anodes. The emission from the discharge was observed with a plane-grating spectrograph and recorded by a photomultiplier tube.In the studied region, the full rotational structure of the 1–1 and 1–5 bands of the B–A system was observed, in total 114 spectral emission lines up to J″=21. All those lines were precisely measured with an estimated accuracy of about 0.0030cm−1, and rotationally analyzed. As a result, many molecular constants were determined for the B1Σ+ and A1Π states in the 12C17O isotopologue. In this paper we have also presented the results of calculations concerning RKR turning points, Franck–Condon factors, relative intensities, and r-centroids for the Ångström band system in the 12C17O molecule. We have also determined the value of the ΔG1/2 vibrational quantum, the isotope shifts, as well as the main, isotopically invariant parameters of the B1Σ+ Rydberg state in the CO molecule within the Born–Oppenheimer approximation.For the A1Π, υ=5 state, considerable irregularities of the rotational structure have been observed and analyzed in detail. Suspected candidates responsible for these perturbations have been identified. The B1Σ+, υ=1 state has been thoroughly analyzed in terms of possible perturbations and it emerged to be completely regular in the 12C17O molecule up to the observed maximum J value.

The A2Δ–X2Π band system of the CD radical

The A2Δ–X2Π, Δv=0 sequence of the CD radical was observed in the 22800–24000cm−1 spectral region using a conventional spectroscopic technique. The CD molecules were formed and excited in a stainless steel hollow-cathode lamp with two anodes and filled with a mixture of He buffer gas and CD4. The emission from the discharge was observed with a plane-grating spectrograph and recorded using a photomultiplier tube. The observed lines were assigned to the 0–0, 1–1, 2–2, and 3–3 bands. In total, 1189 transition wavenumbers were precisely measured, with an estimated accuracy of 0.003cm−1, and rotationally analyzed. In the final global fit, the present data were combined with available high-resolution measurements of the vibration–rotation transitions [Morino et al., J. Mol. Spectrosc. 174 (1995) 123–131] and pure rotational transitions [Brown and Evenson, J. Mol. Spectrosc. 136 (1989) 68–85; Halfen et al., Astrophys. J. 687 (2008) 731–736]. This procedure enabled the extraction of molecular constants for the A2Δ and X2Π states of CD. The equilibrium parameters were compared with the calculations performed using the Born–Oppenheimer approximation, and a slight difference was observed in some cases due to the partial breakdown of the B–O approximation. The electronic isotopic shift, Δνe, for the A–X transition was determined to be 32.105cm-1, and the shift independent of the nuclear mass coefficient, ΔU=64.762(38)cm-1, was also calculated.

High-resolution F T spectrum of A 2 Π r -X 2 Σ + band system of MgCl

The emission spectrum of the A 2 Π r -X 2 Σ + band system of MgCl molecule (360–380 nm) has been recorded on BOMEM DA8 Fourier transform spectrometer at an apodized resolution of 0.035 cm−1. The spectra have been excited under flowing conditions in a demountable stainless steel hollow cathode lamp (400 V, 250 mA) containing anhydrous MgCl2 and Ar. The resulting spectra are very intense and the 0-0, 1-1, 1-0 bands of A 2 Π 1/2-X 2 Σ + sub-transition and the 0-0 band of A 2 Π 3/2-X 2 Σ + sub-transition have been rotationally analyzed. Improved molecular constants have been derived using a least-squares fit program in which optical data of earlier analyzed 0-1 and 0-2 bands (A 2 Π 1/2-X 2 Σ +) was also included. The Λ-doubling constants in the v′ = 0, 1 levels of the A 2 Π 1/2 sub-state are as expected, i.e. p 1 > p 0, where as it is found that the spin-doubling constants of the v″ = 0, 1 and 2 levels of the ground state X 2 Σ +, decrease with the increase in v, i.e. γ 0 > γ 1 > γ 2. This is indicative of the presence of some nearby state, influencing the spin-doubling.

Isotopic exchange processes in cold plasmas of H2/D2 mixtures

Isotope exchange in low pressure cold plasmas of H(2)/D(2) mixtures has been investigated by means of mass spectrometric measurements of neutrals and ions, and kinetic model calculations. The measurements, which include also electron temperatures and densities, were performed in a stainless steel hollow cathode reactor for three discharge pressures: 1, 2 and 8 Pa, and for mixture compositions ranging from 100% H(2) to 100% D(2). The data are analyzed in the light of the model calculations, which are in good global agreement with the experiments. Isotope selective effects are found both in the surface recombination and in the gas-phase ionic chemistry. The dissociation of the fuel gas molecules is followed by wall recycling, which regenerates H(2) and D(2) and produces HD. Atomic recombination at the wall is found to proceed through an Eley-Rideal mechanism, with a preference for reaction of the adsorbed atoms with gas phase D atoms. The best fit probabilities for Eley-Rideal abstraction with H and D are: γ(ER H) = 1.5 × 10(-3), γ(ER D) = 2.0 × 10(-3). Concerning ions, at 1 Pa the diatomic species H(2)(+), D(2)(+) and HD(+), formed directly by electron impact, prevail in the distributions, and at 8 Pa, the triatomic ions H(3)(+), H(2)D(+), HD(2)(+) and D(3)(+), produced primarily in reactions of diatomic ions with molecules, dominate the plasma composition. In this higher pressure regime, the formation of the mixed ions H(2)D(+) and HD(2)(+) is favoured in comparison with that of H(3)(+) and D(3)(+), as expected on statistical grounds. The model results predict a very small preference, undetectable within the precision of the measurements, for the generation of triatomic ions with a higher degree of deuteration, which is probably a residual influence at room temperature of the marked zero point energy effects (ZPE), relevant for deuterium fractionation in interstellar space. In contrast, ZPE effects are found to be decisive for the observed distribution of monoatomic ions H(+) and D(+), even at room temperature. The final H(+)/D(+) ratio is determined to a great extent by proton (and deuteron) exchange, which favours the enhancement of H(+) and the concomitant decrease of D(+).

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.

Excessive broadening of hydrogen Balmer lines for discharge-surface interaction monitoring

A comparative study of the hydrogen Hα line shapes in titanium and stainless steel hollow cathode discharges, run with hydrogen or argon–hydrogen mixture illustrates the possibility of using the excessively broadened part of line profile for heavy particle-cathode surface interaction monitoring.

The microwave spectrum of the FeS radical

The rotational spectrum of the iron monosulfide radical, FeS, was measured in the frequency region of 220–390 GHz with a source-modulated millimeter/submillimeter-wave spectrometer. The radical was efficiently produced in a free space absorption cell by a dc discharge in a mixture of Ar and H 2S with a stainless-steel hollow cathode. Several series of paramagnetic lines were detected with intervals of about 12 GHz. The four series having relatively strong intensity were assigned to FeS in the vibrationally ground state of the X 5Δ i electronic state, two series to that in the vibrationally excited state, and five series presumably to FeS in the electronically excited state, A 5 Σ + . The effective molecular constants were determined for FeS in the X 5Δ i electronic state. The Ω=2 components of the vibrationally ground state showed an apparent shift from the typical pattern of the 5 Δ i state. In addition, the fine structure of the A 5 Σ + state was found to be far from a regular pattern expected for a 5 Σ state. A trial analysis including electronic interaction between the 5 Δ i and 5 Σ states was carried out, but it was not possible to explain the spectral lines of both electronic states simultaneously. Reasons for the heavily perturbed spectral patterns are discussed.