Methods to increase the efficiency of a rare gas–water vapour plasma as a light source are presented: (1) the addition of a second rare gas (2) the use of titanium dioxide to enhance the decomposition of water molecules into hydroxyl and hydrogen; (3) pulse discharge operation to improve the efficiency. Analysis shows that the first two methods can yield an increase in efficiency. Use of the catalyst produced a tangible impact on plasma properties and an increase in efficiency that was experimentally observed and agrees with theoretical estimates. In pulse discharge operation, negative ions that are probably created in the afterglow phase eliminate the desired effect. The data obtained using these three approaches, point towards possible directions for further investigation and predict the expected results in case of successful implementation.

The method of using similarity laws for the study of a physical system in which some form of similarity laws exist is proposed. The example of such a system is the positive column of a gas discharge. Here, two types of similarity laws are considered: 'classical' laws and new laws that are valid for a mixture of a buffer gas and an ionization additive. New data obtained with the application of the method are presented.

The excitation cross-sections of the OH-radical band A(2) Sigma(+) -> X-2 (v' = 0 -> v '' = 0, v' = 1 -> v '' = 1) were measured. OH-radicals were formed during dissociation of water molecules by electron impact in the conditions of crossing of supersonic molecular and electron beams in the energy range 10-120 eV. Measurements were conducted at temperatures of 50, 80 and 200 K. It was shown that the excitation function had a sharp maximum in the region of low energies (at 16 eV) and an extended plateau up to 120 eV. It is proved that there are two channels of molecule dissociation with formation OH (A(2) Sigma(+)) through excitation of either the triplet b(3)A(1) or the singlet B(1)A(1) states of H2O molecules. The form of the excitation function essentially depends on the temperature of water vapours in the beam. With the decrease of the water molecule temperature the height of the plateau in the region 30-120 eV decreases in comparison with that of the peak at 16 eV. The absolute value of the excitation cross-section of the OH band at the temperature 50 K has been measured. It is equal to (1.6 +/- 0.5) x 10(-18) cm(2) in the maximum at 16 eV. The ratio of cross-sections of bands 1-1 and 0-0 weakly depends on the energy of the exciting electron in the range 12-120 eV and is equal to 0.28 +/- 0.05. The appearance threshold is equal to (9.1 +/- 0.5) eV.

Signals from ions forming in a supersonic molecular beam consisting of an argon-water vapor mixture are measured as functions of the exciting electron energy in the range to 120 eV. The thresholds of electron impact excitation of (H2O) n − 1H+ and Ar n (H2O m + clusters are determined for the first time. It is found that the proton-hydroxyl group binding energy decreases considerably both in the case of water molecule clustering and when mixed Ar n (H2O) m clusters arise.

The electric field strength, electrode fall voltage, light emission characteristics and efficiency of a (Ar + H2O) dc discharge as functions of water vapour content, argon pressure and electric current are presented. The data show that the main processes of 306.4 nm OH band generation are (1) a collision between an excited argon atom and a water molecule with simultaneous excitation of OH into the A(2)Sigma(+) state and (2) electron excitation of a ground state hydroxyl molecule produced by a quenching process from a water molecule. Electric field strength measurements make it possible to conclude that the light production efficiency of the plasma under study can reach 35 lm W-1. It is possible, with these data, to propose a model of the plasma in question having reasonable accordance with the experiment and show the way to further increase the efficiency.

Spectral and electrical characteristics of a low pressure dc discharge formed from a mixture of one of the rare gases Ne, Ar or Kr plus water vapour are studied. Water vapour is only a minor additive to the rare gas. It has been shown that enhanced emission of the OH 306.4 nm band is registered from the discharge of Ar mixed with water vapour. Plasmas from the other investigated rare gases yielded considerably less OH 306.4 nm emission. Data about consumed electric power, spectra and relative efficiencies are presented.

Journal of the American College of Surgeons: April 2007 - Volume 204 - Issue 4 - p 726 doi: 10.1016/j.jamcollsurg.2007.01.055

It is found that the composition of a pulsed supersonic molecular beam depends on the preparation conditions of the initial mixture containing water molecules and argon atoms. The mass spectra of the molecular beam components are obtained, and the time evolution of the signal intensities for some of the ions ( T form) is traced. It is shown that stable water complexes remaining intact during supersonic flow of the mixture into a vacuum may form depending on the water partial pressure.

The time resolved and DC photoconduction characteristics of Si nanowire devices are described. Si nanowires with diameters ranging from 20-100 nm were grown using the vapor-liquid-solid (VLS) growth mechanism under standard conditions and devices were fabricated in a back-gate field effect transistor (FET) configuration using simple photolithography. It is shown that under certain biasing conditions, illumination with light from light emitting diodes with wavelengths ranging from 480 nm to 625 nm causes changes in current as high as 4%. On the other hand, illumination by a broadband incandescent source causes a ∼4.1% percent change in current. Photoconductive decay curves show bi- and tri-exponential behavior, indicative of multiple potential recombination mechanisms occurring within the Si nanowire devices. p-n doped Si nanowires show similar behavior. Studies under various drain and gate voltages provides insight into the proposed mechanism. It is argued that the Shottky barrier plays a strong role in the observed photoconduction process in these wires, as do transitions involving surface and deep level trap states.