Atmospheric Helium Capillary Dielectric Barrier Discharge for Soft Ionization: Determination of Atom Number Densities in the Lowest Excited and Metastable States

The populations of the lowest excited helium states 2s ³S₁, 2s ¹S, 2p ³P⁰_J, and 2p ¹P⁰ created in an atmospheric helium capillary dielectric barrier discharge were determined by means of optical emission spectroscopy. The emitted intensities of 388, 501, 587, and 667 nm lines were measured side-on and end-on with respect to the discharge axis. The comparison of optically thin side-on spectra with end-on spectra, which exhibited the absorption effects in the line kernels, enabled the determination of the average values of the number densities <i>n</i>₁ in the considered He states along the plasma length <i>L</i>. The field of the theoretical profiles for a series of the <i>n</i>₁<i>L</i> parameters pertinent to the experimental conditions was calculated for each line. By introducing the experimental data into the field of calculated curves, <i>n</i>₁<i>L</i> corresponding to the particular state could be obtained. The measurements of the emission profiles were done as a function of the discharge voltage in the range covering homogeneous as well as filamentary DBD operation mode. Due to nonuniformity of the excited atom density distribution along the plasma, the values of <i>n</i>₁ could be obtained only in the homogeneous operation mode where the nonuniformity was small. The following maximum values were found for the number densities in the investigated states: <i>n</i>₁^av (2s ³S₁) = (2.9 ± 1.1) × 10¹³ cm^–3, <i>n</i>₁^av (2s ¹S) = (1.4 ± 0.5) × 10¹³ cm^–3, <i>n</i>₁^av (2p ³P⁰_J) = (1.1 ± 0.4) × 10¹³ cm^–3, <i>n</i>₁^av (2p ¹P⁰) = (4.2 ± 1.6) × 10¹² cm^–3, and they represent the average populations along the plasma column in the capillary

Atmospheric Helium Capillary Dielectric Barrier Discharge for Soft Ionization: Determination of Atom Number Densities in the Lowest Excited and Metastable States

The populations of the lowest excited helium states 2s ³S₁, 2s ¹S, 2p ³P⁰_J, and 2p ¹P⁰ created in an atmospheric helium capillary dielectric barrier discharge were determined by means of optical emission spectroscopy. The emitted intensities of 388, 501, 587, and 667 nm lines were measured side-on and end-on with respect to the discharge axis. The comparison of optically thin side-on spectra with end-on spectra, which exhibited the absorption effects in the line kernels, enabled the determination of the average values of the number densities <i>n</i>₁ in the considered He states along the plasma length <i>L</i>. The field of the theoretical profiles for a series of the <i>n</i>₁<i>L</i> parameters pertinent to the experimental conditions was calculated for each line. By introducing the experimental data into the field of calculated curves, <i>n</i>₁<i>L</i> corresponding to the particular state could be obtained. The measurements of the emission profiles were done as a function of the discharge voltage in the range covering homogeneous as well as filamentary DBD operation mode. Due to nonuniformity of the excited atom density distribution along the plasma, the values of <i>n</i>₁ could be obtained only in the homogeneous operation mode where the nonuniformity was small. The following maximum values were found for the number densities in the investigated states: <i>n</i>₁^av (2s ³S₁) = (2.9 ± 1.1) × 10¹³ cm^–3, <i>n</i>₁^av (2s ¹S) = (1.4 ± 0.5) × 10¹³ cm^–3, <i>n</i>₁^av (2p ³P⁰_J) = (1.1 ± 0.4) × 10¹³ cm^–3, <i>n</i>₁^av (2p ¹P⁰) = (4.2 ± 1.6) × 10¹² cm^–3, and they represent the average populations along the plasma column in the capillary

Atmospheric Helium Capillary Dielectric Barrier Discharge for Soft Ionization: Determination of Atom Number Densities in the Lowest Excited and Metastable States

The populations of the lowest excited helium states 2s ³S₁, 2s ¹S, 2p ³P⁰_J, and 2p ¹P⁰ created in an atmospheric helium capillary dielectric barrier discharge were determined by means of optical emission spectroscopy. The emitted intensities of 388, 501, 587, and 667 nm lines were measured side-on and end-on with respect to the discharge axis. The comparison of optically thin side-on spectra with end-on spectra, which exhibited the absorption effects in the line kernels, enabled the determination of the average values of the number densities <i>n</i>₁ in the considered He states along the plasma length <i>L</i>. The field of the theoretical profiles for a series of the <i>n</i>₁<i>L</i> parameters pertinent to the experimental conditions was calculated for each line. By introducing the experimental data into the field of calculated curves, <i>n</i>₁<i>L</i> corresponding to the particular state could be obtained. The measurements of the emission profiles were done as a function of the discharge voltage in the range covering homogeneous as well as filamentary DBD operation mode. Due to nonuniformity of the excited atom density distribution along the plasma, the values of <i>n</i>₁ could be obtained only in the homogeneous operation mode where the nonuniformity was small. The following maximum values were found for the number densities in the investigated states: <i>n</i>₁^av (2s ³S₁) = (2.9 ± 1.1) × 10¹³ cm^–3, <i>n</i>₁^av (2s ¹S) = (1.4 ± 0.5) × 10¹³ cm^–3, <i>n</i>₁^av (2p ³P⁰_J) = (1.1 ± 0.4) × 10¹³ cm^–3, <i>n</i>₁^av (2p ¹P⁰) = (4.2 ± 1.6) × 10¹² cm^–3, and they represent the average populations along the plasma column in the capillary

Atmospheric Helium Capillary Dielectric Barrier Discharge for Soft Ionization: Determination of Atom Number Densities in the Lowest Excited and Metastable States

The populations of the lowest excited helium states 2s ³S₁, 2s ¹S, 2p ³P⁰_J, and 2p ¹P⁰ created in an atmospheric helium capillary dielectric barrier discharge were determined by means of optical emission spectroscopy. The emitted intensities of 388, 501, 587, and 667 nm lines were measured side-on and end-on with respect to the discharge axis. The comparison of optically thin side-on spectra with end-on spectra, which exhibited the absorption effects in the line kernels, enabled the determination of the average values of the number densities <i>n</i>₁ in the considered He states along the plasma length <i>L</i>. The field of the theoretical profiles for a series of the <i>n</i>₁<i>L</i> parameters pertinent to the experimental conditions was calculated for each line. By introducing the experimental data into the field of calculated curves, <i>n</i>₁<i>L</i> corresponding to the particular state could be obtained. The measurements of the emission profiles were done as a function of the discharge voltage in the range covering homogeneous as well as filamentary DBD operation mode. Due to nonuniformity of the excited atom density distribution along the plasma, the values of <i>n</i>₁ could be obtained only in the homogeneous operation mode where the nonuniformity was small. The following maximum values were found for the number densities in the investigated states: <i>n</i>₁^av (2s ³S₁) = (2.9 ± 1.1) × 10¹³ cm^–3, <i>n</i>₁^av (2s ¹S) = (1.4 ± 0.5) × 10¹³ cm^–3, <i>n</i>₁^av (2p ³P⁰_J) = (1.1 ± 0.4) × 10¹³ cm^–3, <i>n</i>₁^av (2p ¹P⁰) = (4.2 ± 1.6) × 10¹² cm^–3, and they represent the average populations along the plasma column in the capillary

Atmospheric Helium Capillary Dielectric Barrier Discharge for Soft Ionization: Determination of Atom Number Densities in the Lowest Excited and Metastable States

The populations of the lowest excited helium states 2s ³S₁, 2s ¹S, 2p ³P⁰_J, and 2p ¹P⁰ created in an atmospheric helium capillary dielectric barrier discharge were determined by means of optical emission spectroscopy. The emitted intensities of 388, 501, 587, and 667 nm lines were measured side-on and end-on with respect to the discharge axis. The comparison of optically thin side-on spectra with end-on spectra, which exhibited the absorption effects in the line kernels, enabled the determination of the average values of the number densities <i>n</i>₁ in the considered He states along the plasma length <i>L</i>. The field of the theoretical profiles for a series of the <i>n</i>₁<i>L</i> parameters pertinent to the experimental conditions was calculated for each line. By introducing the experimental data into the field of calculated curves, <i>n</i>₁<i>L</i> corresponding to the particular state could be obtained. The measurements of the emission profiles were done as a function of the discharge voltage in the range covering homogeneous as well as filamentary DBD operation mode. Due to nonuniformity of the excited atom density distribution along the plasma, the values of <i>n</i>₁ could be obtained only in the homogeneous operation mode where the nonuniformity was small. The following maximum values were found for the number densities in the investigated states: <i>n</i>₁^av (2s ³S₁) = (2.9 ± 1.1) × 10¹³ cm^–3, <i>n</i>₁^av (2s ¹S) = (1.4 ± 0.5) × 10¹³ cm^–3, <i>n</i>₁^av (2p ³P⁰_J) = (1.1 ± 0.4) × 10¹³ cm^–3, <i>n</i>₁^av (2p ¹P⁰) = (4.2 ± 1.6) × 10¹² cm^–3, and they represent the average populations along the plasma column in the capillary

Atmospheric Helium Capillary Dielectric Barrier Discharge for Soft Ionization: Determination of Atom Number Densities in the Lowest Excited and Metastable States

The populations of the lowest excited helium states 2s ³S₁, 2s ¹S, 2p ³P⁰_J, and 2p ¹P⁰ created in an atmospheric helium capillary dielectric barrier discharge were determined by means of optical emission spectroscopy. The emitted intensities of 388, 501, 587, and 667 nm lines were measured side-on and end-on with respect to the discharge axis. The comparison of optically thin side-on spectra with end-on spectra, which exhibited the absorption effects in the line kernels, enabled the determination of the average values of the number densities <i>n</i>₁ in the considered He states along the plasma length <i>L</i>. The field of the theoretical profiles for a series of the <i>n</i>₁<i>L</i> parameters pertinent to the experimental conditions was calculated for each line. By introducing the experimental data into the field of calculated curves, <i>n</i>₁<i>L</i> corresponding to the particular state could be obtained. The measurements of the emission profiles were done as a function of the discharge voltage in the range covering homogeneous as well as filamentary DBD operation mode. Due to nonuniformity of the excited atom density distribution along the plasma, the values of <i>n</i>₁ could be obtained only in the homogeneous operation mode where the nonuniformity was small. The following maximum values were found for the number densities in the investigated states: <i>n</i>₁^av (2s ³S₁) = (2.9 ± 1.1) × 10¹³ cm^–3, <i>n</i>₁^av (2s ¹S) = (1.4 ± 0.5) × 10¹³ cm^–3, <i>n</i>₁^av (2p ³P⁰_J) = (1.1 ± 0.4) × 10¹³ cm^–3, <i>n</i>₁^av (2p ¹P⁰) = (4.2 ± 1.6) × 10¹² cm^–3, and they represent the average populations along the plasma column in the capillary

Systematic Comparison between Half and Full Dielectric Barrier Discharges Based on the Low Temperature Plasma Probe (LTP) and Dielectric Barrier Discharge for Soft Ionization (DBDI) Configurations

Dielectric barrier discharge (DBD)-based analytical applications have experienced rapid development in recent years. DBD designs and parameters and the application they are used for can vary considerably. This leads to a diverse field with many apparently unique systems that are all based on the same physical principle. The most significant changes among DBDs used for chemical analysis are in how the discharge electrodes are separated from the ignited discharge gas. While the official definition of a DBD states that at least one electrode has to be covered by a dielectric to be considered a DBD, configurations with both electrodes covered by dielectric layers can also be realized. The electrode surface plays a major role in several plasma-related technical fields, surface treatment or sputtering processes, for example, and has hence been studied in great detail. Analytical DBDs are often operated at low power and atmospheric pressure, making a direct transfer of insight and know-how gained from the aforementioned well-studied fields complicated. This work focuses on comparing two DBD configurations: the low temperature plasma probe (LTP) and the dielectric barrier discharge for soft ionization (DBDI). The LTP is representative of a DBD with one covered electrode and the DBDI of a design in which both electrodes are covered. These two configurations are well suited for a systematic comparison due to their similar geometric designs based on a dielectric capillary

Soft Argon–Propane Dielectric Barrier Discharge Ionization

Dielectric barrier discharges (DBDs) have been used as soft ionization sources (DBDI) for organic mass spectrometry (DBDI-MS) for approximately ten years. Helium-based DBDI is often used because of its good ionization efficiency, low ignition voltage, and homogeneous plasma conditions. Argon needs much higher ignition voltages than helium when the same discharge geometry is used. A filamentary plasma, which is not suitable for soft ionization, may be produced instead of a homogeneous plasma. This difference results in N₂, present in helium and argon as an impurity, being Penning-ionized by helium but not by metastable argon atoms. In this study, a mixture of argon and propane (C₃H₈) was used as an ignition aid to decrease the ignition and working voltages, because propane can be Penning-ionized by argon metastables. This approach leads to homogeneous argon-based DBDI. Furthermore, operating DBDI in an open environment assumes that many uncharged analyte molecules do not interact with the reactant ions. To overcome this disadvantage, we present a novel approach, where the analyte is introduced in an enclosed system through the discharge capillary itself. This nonambient DBDI-MS arrangement is presented and characterized and could advance the novel connection of DBDI with analytical separation techniques such as gas chromatography (GC) and high-pressure liquid chromatography (HPLC) in the near future