Experimental and numerical study of self-induced transparency in a neon absorber

Self-induced transparency on the neon transition 2s ₂(J=1)–2p ₄(J=2) is studied both experimentally by investigating the propagation of 3-nsec laser pulses at 1.15 µm in an absorber discharge and theoretically by a numerical integration of Bloch's equations and the wave equation.—The application of linearly and circularly polarized light corresponds to the interaction with a quasi-nondegenerate and degenerate transition, respectively. Pulse shapes, delays, and transmittancevs. input peak intensity are found in quantitative agreement with the calculated data. While with linear light polarization all SIT characteristics clearly appear, with circular polarization the pulse break-up and the oscillation of transmittance due to optical nutations are washed out.—The homogeneous linewidth derived from pulse delay data agrees with the value from conventional measurements. The results prove SIT useful as a quantitative spectroscopic method.     

Experimental and numerical study of self-induced transparency in a neon absorber

Self-induced transparency on the neon transition 2s ₂(J=1)–2p ₄(J=2) is studied both experimentally by investigating the propagation of 3-nsec laser pulses at 1.15 µm in an absorber discharge and theoretically by a numerical integration of Bloch's equations and the wave equation.—The application of linearly and circularly polarized light corresponds to the interaction with a quasi-nondegenerate and degenerate transition, respectively. Pulse shapes, delays, and transmittancevs. input peak intensity are found in quantitative agreement with the calculated data. While with linear light polarization all SIT characteristics clearly appear, with circular polarization the pulse break-up and the oscillation of transmittance due to optical nutations are washed out.—The homogeneous linewidth derived from pulse delay data agrees with the value from conventional measurements. The results prove SIT useful as a quantitative spectroscopic method.Work supported by the Deutsche Forschungsgemeinschaft     

Cathode-current ratio in a reflective hollow-cathode discharge

The current ratio has been examined for hollow and planar cathodes as affected by the gas type and flow rate; a model is proposed that gives an expression in qualitative agreement with experiment.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 64–67, April, 1990.We are indebted to E. M. Oks for assistance in the experiments and valuable comments.     

Experimental observation of interatomic coulombic decay in neon dimers

Recently Cederbaum et al. [Phys. Rev. Lett. 79, 4778 (1997)]] predicted a new decay channel of excited atoms and molecules termed interatomic Coulombic decay (ICD). In ICD the deexcitation energy is transferred via virtual photon exchange to a neighboring atom, which releases it by electron emission. We report on an experimental observation of ICD in 2s ionized neon dimers. The process is unambiguously identified by detecting the energy of two Ne1+ fragments and the ICD electron in coincidence, yielding a clean, background free experimental spectral distribution of the ICD electrons.     

Metal-atom concentration formation in a hollow-cathode discharge

Monte Carlo methods have been applied to the concentration pattern in a hollowcathode discharge, and approximate formulas are derived for the concentrations of the sputtered and/or evaporated atoms. Some standard experimental relationships for the sputtered concentrations are explained.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 92–96, March, 1989.     

Discharge initiation in a hollow-cathode plasma source of electrons

Experimental results on discharge initiation in a hollow-cathode plasma source of electrons are reported. The discharge is initiated by ions flowing out from the accelerating gap into the discharge region. The ions are generated by a high-voltage glowing discharge occurring in the accelerating gap at a pressure of more than 2 Pa and a voltage of no less than 2 kV. It is shown that an increase in the ion-electron emission coefficient, which can be raised by properly choosing the gas-metal pair, decreases the threshold ion current initiating the discharge at a fixed discharge voltage.     

Analysis of a hollow-cathode reflex discharge in a hydrocarbon flow

Variation of parameters of a reflex discharge with a hollow cathode operating continuously in propane with a flow rate of 1.3–5.6 (m³ mPa)/s and a discharge current of 0.1–0.4 A is analyzed. It is shown that for a hydrocarbon flow rate of 2.4 (m³ mPa)/s and higher, an increase in the discharge voltage takes place after a time interval depending on the discharge current and gas pressure; this is explained by the formation of coating of the dissociation products of hydrocarbon molecules on the electrodes of the discharge chamber. An increase in the thickness of the carbon coating of the cathodes with time and their charging with ions lead to electric breakdown of coatings and the formation of cathode spots. The oscillograms of the discharge current and voltage indicate a short-term transformation of the glow discharge into the arc discharge. The energy spectra of ions emerging from the discharge are measured, and the effect of the discharge current and the gas flow rate on the energy spread of ions is analyzed. The operation time of the discharge in hydrocarbon after which the cleaning of the discharge chamber is required is determined. The possibility of using an ion source based on the reflex discharge with a hollow cathode for technological purposes is established.     

Laser diagnostics of a low-pressure hollow-cathode arc

We report the use of resonance fluorescence induced by a repetitively pulsed tunable dye laser in measuring electron collisional transfer rates between fine-structure levels, electron density and neutral particle temperature in a low-pressure hollow-cathode arc. Excitation by a narrow bandwidth laser is analyzed to obtain correct interpretation of the results. A power-broadening formula, which is valid for large saturation parameters, has been derived and experimentally verified.     

空心阴极灯中镧原子消多普勒光谱

我们在自制的La-Kr阴极灯中,用内调制、消多普勒荧光法研究了镧原子一些能级的超精细结构.据我们所知,其中20197.34cm~(-1)、21447.86cm~(-1)能级的超精细结构常数A、B尚无报道,这还是第一次.此外,还获得了线宽小于40MHz的线型和来自公共低能级的所有交岔线(Cross-Over line).对阴极灯中原子光谱特性进行了研究.     

Characterizing passive coherent population trapping resonance in a cesium vapor cell filled with neon buffer gas

We present a pair of phase-locked lasers with a 9.2-GHz frequency difference through the injection locking of a master laser to the RF-modulation sideband of a slave diode laser. Using this laser system, a coherent population trapping (CPT) signal with a typical linewidth of ～ 182 Hz is obtained in a cesium vapor cell filled with 30 Torr (4kPa) of neon as the buffer gas. We investigate the influence of the partial pressure of the neon buffer gas on the CPT linewidth, amplitude, and frequency shift. The results may offer some references for CPT atomic clocks and CPT atomic magnetometers.     

Modes of a Ne-H2 laser employing a hollow-cathode discharge

An Ne-H₂ laser employing the 2s-2p transition in Ne is examined at current densities up to 300 ma/cm². The H₂ removes metastable Ne atoms and reduces the rate of excitation of the 2p level, so the discharge currents may be raised considerably. The gain at 11 143 Å is measured as a function of discharge current for near-optimal conditions.     

Laser excited population redistribution in the 2p3p multiplet in neon

Using neon hollow cathode lamp and employing laser optogalvanic technique, we have studied population redistribution in the 2p⁵3p multiplet. The spectra recorded in the laser energy region of 23300 cm^− 1 -23600 cm^− 1 show transitions originating from both the laser excited levels as well as from an adjacent level whose population builds up as a result of collisional deactivation. Employing the optical delay technique, we have been able to extract decay rates associated with the collisional population mixing of the p levels.     

The ion emissivity of a hollow-cathode non-self-sustained glow discharge

The paper presents the results of research of the mass-charge state of an ion beam extracted from the plasma of a hollow-cathode non-self-sustained glow discharge with a time-of-flight spectrometer. The influence of the discharge parameters on the mass-charge state of the beam is discussed. It has been shown that a drop in discharge operating voltage allows a substantial decrease in the metal-ion fraction of the beam, and an increase in discharge current results in an increase in the average charge of gas ions and in an increase in the metal fraction of the beam. Institute of High Current Electronics. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 14–20, February, 2000.     

Nitrogen atom energy distributions in a hollow-cathode planar sputtering magnetron

Energy distributions of nitrogen atoms (N) in a hollow-cathode planar sputtering magnetron were obtained by use of optical emission spectroscopy. A characteristic line, N I 8216.3 A, well separated from molecular nitrogen emission bands, was identified. Jansson's nonlinear spectral deconvolution method, refined by minimization of chi(2)(w), was used to obtain the optimal deconvolved spectra. These showed nitrogen atom energies from 1 eV to beyond 500 eV. Based on comparisons with VFTRIM computer code results, it is proposed that the energetic N's are generated from N+2 ions after these ions are accelerated through the sheath and dissociatively reflect from the cathode.