Second Positive Band Of Nitrogen Research Articles

Characteristics of capacitively coupled RF helium/neon discharges in a hollow fiber

Capacitively coupled radio-frequency microplasmas are produced in hollow fibers with an inner diameter of hundreds of micrometers powered by an 80-MHz power supply. Considering the narrow space of the hollow core, optical emission spectrometry is used to obtain the spatially resolved characteristics of the microplasmas. The rotational temperature, excitation temperature, and electron density of microplasmas are determined based on the second positive band of nitrogen, the atomic spectra of bulk neutral particles of plasmas, and the Hβ line of the hydrogen Balmer series, respectively. In our experiments, the rotational temperature, excitation temperature, and electron density of typical inert gases helium and neon are in the ranges of 300–500 K, 7000–9500 K, and 1013 cm−3, respectively. The results obtained with different external parameters of power and pressure show that the light emission intensity increases with power and pressure. The distributions of the rotational temperature, excitation temperature, and electron density of the microplasmas are almost constant over the gap between the electrodes. These distributions are mostly insensitive to the change of power and pressure in single-component plasmas. The characteristics of mixed plasmas are also investigated. The plasma with a larger helium content possesses higher excitation temperature and lower rotational temperature and electron density than those of the plasma with a lower helium content.

Spectroscopic investigation of the bipolar pulsed discharge in water-air mixture

Emission spectrum of the bipolar pulsed discharge in water-air mixture has been measured in the near-ultraviolet (UV) region using an Inspectrum 300 charge-coupled device (CCD) spectrograph. Effects of several parameters including peak-to-peak voltage, pulse repetitive frequency, etc., on the relative UV radiation intensity have been investigated. Experimental results show that bipolar pulsed discharge in water-air mixture emits strong UV radiation. The emission spectrum of the discharge has a wide range. The applied peak-to-peak voltage, pulse repetitive frequency, and air flow rate have positive effect on the relative intensity of the second positive band of nitrogen at 337.1 nm. However, solution conductivity has negative effect

Structure of Low-Frequency Helium Glow Discharge at Atmospheric Pressure between Parallel Plate Dielectric Electrodes

Atmospheric-pressure helium glow discharge at 100 kHz between parallel plate dielectric electrodes is studied experimentally and theoretically. Experimental work was carried out by spatiotemporal optical emission spectroscopy to examine the behavior of electrons. The emission from helium atoms revealed the behavior of high-energy electrons (above 22 eV), while the emission from the second positive band of nitrogen revealed the behavior of medium-energy electrons (11–20 eV). Theoretical work was carried out using a one-dimensional fluid model with local field approximation under the same discharge conditions as the experimental one. It was clarified that i) the discharge structure is essentially the same as that in low-pressure glow discharge, ii) ionization by secondary electrons from the cathode is essential for sustaining the discharge, and iii) ionization occurs at low electric field (about 30 Td). This last property is important for conducting “moderate” ionization for stable glow discharge at atmospheric pressure in the absence of localized discharge columns.

Excitation of the C 3 Pi u state of N2 by electron impact in the near-threshold region

The total cross section for excitation of the nu '=0, 1, 2 vibrational levels and the total electronic cross section of the C3 Pi u state of nitrogen have been determined for incident electron energies from threshold at 11.03 eV to 17.5 eV. The emission cross section of the (0,0) line (337 nm) of the second positive band of nitrogen has been also obtained in this energy region. Strong non-Franck-Condon excitation of vibrational levels has been observed. The present data are compared with previous experimental and theoretical results.

Spectra of a glow discharge in flowing nitrogen

The visible spectrum of the positive column of a glow discharge in flowing nitrogen was investigated. There is experimental evidence that the emission spectra depend on the flow velocity and that the changes in the intensity of the first positive and second positive bands of nitrogen are quite different. The results cannot be explained by one-step excitation of electronic levels from the ground state. On the other hand they are consistent with the assumption of stepwise excitation and of atomic recombination to electronically excited molecular levels.

Picosecond uv laser pulses from gas discharges in pure nitrogen at pressures up to 6 atm

Single picosecond laser pulses in the second positive band of nitrogen are observed from high-pressure gas discharges with traveling-wave excitation. The gas discharge is operated in pure nitrogen and without preionization. The pulse duration decreases from 300 psec at 1 atm to 50 psec at 6 atm.

Quasi-cw laser emission from the second positive band of nitrogen

Quasi-cw laser emission from the second positive band of nitrogen

Quasi-cw laser emission from the second positive band of nitrogen

Experimental results are presented for the observation of a second positive nitrogen laser that has a pulse length much longer than the radiative lifetime of the upper laser level. Preliminary measurements of the temporal behavior of this laser indicate that it was operating in a quasi-continuous-wave manner and, in addition, the laser output was extremely sensitive to the alignment of the optical cavity placed around the discharge tube.

Electron excitation of the (0,0) second positive band of nitrogen from threshold to 1000 eV: M Imami and W L Borst,J Chem Phys, 61 (3), 1976, 1115–1117.

Electron excitation of the (0,0) second positive band of nitrogen from threshold to 1000 eV: M Imami and W L Borst,J Chem Phys, 61 (3), 1976, 1115–1117.

Electron excitation of the (0,0) second positive band of nitrogen from threshold to 1000 eV

The excitation of the 2P G (0,0) band of nitrogen (λ3371) by electron impact was studied from threshold (11 eV) to 1000 eV. In view of the serious discrepancies in the existing cross section measurements for this band at higher energies (> 30 eV), the effects due to high pressures and secondary electrons were carefully studied. Secondary electron effects were monitored by scanning the luminosity profiles in the collision chamber with a moveable optical detector assembly. The signal count rates were also monitored as a function of pressure. As a result of these checks, the present measurements were carried out at pressures in the 10−5 torr range. In order to increase the signal count rates at these pressures and high electron energies, the collision chamber was given the shape of an ellipsoid with highly polished interior surfaces. The electron gun was of the electrostatically focussed type. The signal count rates were compared with those from the 1N G (0,0) band at λ3914, for which the cross section is well established. As a result, it was found that the cross section for the 2P G (0,0) band decreases rapidly with increasing energy, but not rapidly enough to yield the expected E−3 dependence. The cross section has a value of 1.3×10−19 cm2 at 100 eV, which is about an order of magnitude smaller than most existing measurements.

The phenomenon of 'spreading',outside an electron beam, of the first and second positive bands of nitrogen

Using a well defined electron beam to excite nitrogen in a collision chamber, observations made of the light emitted from the regions of the chamber outside the geometry of the beam showed that the first and second positive band systems were present and also the second negative band system to a lesser extent. The process N2(A3 Sigma +u)+N2(A3 Sigma +u)+N2(x1 Sigma +g) to N2(C3 Pi u)+N2(X1 Sigma +g)+N2(x1 Sigma +g) is proposed to account for the spreading of the second positive bands. This process also contributes to the spread of the first positive bands and is supplemented by the process suggested in 1934 by Thompson and Williams so that the larger spread is accounted for.

Absolute cross sections for electron excitation of the second positive bands of nitrogen

Absolute excitation cross sections for the emission of the second positive bands of nitrogen under electron impact have been obtained. Peak level cross sections for the νprime = 0, 1, 2 levels of the c 3IIu state were found to be, respectively, 23·5 × 10-18 cm2, 14·4 × 10-18 cm2 and 4·9 × 10-18 cm2. Good agreement is found with the theoretical A coefficients for the relative intensities of the different vibrational bands. The results are compared with those of other workers and various secondary effects which were observed are discussed.

Effect of Irradiation on the Intensity Distribution of the Second Positive Nitrogen Bands excited in a Nitrogen Ozonizer

MORE exact measurements have now been made of the changes in the relative intensities of several bands of the second positive system of nitrogen, brought about by irradiation with the 3650–3660 A. group of mercury radiations, using an ozonizer discharge tube excited under conditions yielding the maximum negative Joshi effect when the pressure of the gas is 20 mm. These confirm, in general, the results of preliminary investigations1 and show further that the percentage decreases of intensity are in the following order of bands: In sequences : (1,4) > (0,3) ; (1,3) > (0,2) In progressions : (0,3) > (0,2) > (0,1) ; (1,4) > (1,3). The results show that a change in the relative intensity distribution of the second positive bands of nitrogen is thus brought about, not only in sequences but also in progressions.

Erratum to: Intensity variations in the first positive and second positive bands of nitrogen excited by high frequency oscillations

A discharge tube containing air at low pressure is excited by h.f. frequency oscillations from a modified Hartley circuit. It is observed that there is a critical frequency of exciting oscillations, namely 735 k.c.|sec. below which the colour of the discharge is pinkish red and above which the colour is orange yellow. The spectrum of the discharge in the visible region consists of the first positive and second positive bands of nitrogen. A study of some of these bands as regards their intensity variation depending upon the frequency of exciting oscillations is made. It is found that the first positive bands at 5371, 5406 and 5441 A decrease in intensity as the frequency of exciting oscillations is reduced from 790 to 680 k.c.|sec. The second positive bands at 4355, 4417, 4490, 4649, 4724, 4815 and 4917 A on the other hand, increase in intensity under the same conditions. The results are in harmony with the theoretical conceptions, regarding such phenomena and allow us to conclude that in the present experiments an energy of 15 e.v. is available for excitation when oscillations of frequency 735 k.c.|sec. are used.

Intensity variations in the first positive and second positive bands of nitrogen excited by high frequency oscillations

Intensity variations in the first positive and second positive bands of nitrogen excited by high frequency oscillations

Existence of the Bands 2963, 2977 in Night Sky Spectra

THE list of wave-lengths in the light of the night sky, which was reported by Gauzit1 two years ago, includes the two second positive bands of nitrogen 2963 and 2977 with an intensity ratio of 2 to 1. Since those bands lie in the region of the great Hartley absorption band of ozone, the reality of those observations could readily be open to question. The importance of additional evidence concerning this problem is understood when it is pointed out that the shortest auroral radiation which has been reported is the second positive band at 3110.

Spectrographic Observations of Infra-Red Lines in the Auroral Spectrum

I HAVE read with great interest Prof. L. Vegard's recent communication1 on this subject, in which he reports that in the auroral spectrum in the infra-red he has found two bands, a strong one at 7883 A. and a weak one at 8095 A., with sharp edges towards longer wave-lengths. Prof. Vegard considers that if the auroral green line is to be identified with the oxygen line at 5577 A., it is expected that other oxygen triplets, 7772-74-75, 8233-30-22, 7952-50-47, and 7481-79-77, will appear in this region, but none of these could be identified with the observed auroral lines. Taking into consideration the high intensities of these two bands, and the emission of the second positive bands of nitrogen in the auroral spectrum, he has interpreted these two bands as the appearances of the first positive bands of nitrogen with the special distribution of intensity.

The General Electric Type S-1 Lamp as a Spectroscopic Source

The possibilities presented by the General Electric type S-1 lamp as a spectroscopic source have been investigated by employing lamps filled with argon, hydrogen, helium, neon and carbon dioxide. Nitrogen-filled lamps yielded the second positive bands of nitrogen greatly modified in form from that usually obtained from a Geissler tube discharge. The spectra of hydrogen-filled lamps which also contained mercury showed the mercury hydride bands while the spectra of carbon dioxide-filled lamps gave evidence only of the third positive bands of Deslandres. Further investigation of the more quantitative aspects of the problem will be studied.