Spectroscopic Temperature Measurements for a Direct Current Arcjet Diamond Chemical Vapor Deposition Reactor

The diamond thin filmcommercial market isprojected to exceed one billion dollars by the year 2000. Potential applications of diamond thin films range from cutting tools to electronics tomedical devices. The explosion ofinterest in this fieldresults from the extreme properties diamond possesses: itis the hardest material known toman and yet, has a coefficient of friction similar to Teflon;its ability to conduct heat is five times that of copper; and diamond is completely inert. However, despite the tremendous economic incentive, there are still several technological barriers preventing diamond filmscale-up to commercial production. Included among these are a fundamental understanding of the gas phase chemistry leading to diamond filmformation and the lack of a reliable insitu, on-line Chemical Vapor Deposition (CVD)monitoring capability. Here we describe the use of optical emission spectroscopy (OES) as a possible direct current CVD plasma jet on-line monitor. Specifically, OES spectra from the C2 radical, an intermediate species in the diamond CVD process, is utilized to obtain plasma gas temperatures insitu. Additionally, the reliability of a plasma gas temperature determined fromOES is examined withLaser-Induced-Fluorescence (LIF)

Using LabVIEW to Synchronize an Infrared Diode Laser Spectrometer with a Pulsed Supersonic Jet Expansion

We describe software developed with LabVIEW to provide operational control for an in-house infrared diode laser spectrometer that has been combined with a pulsed supersonic jet expansion sample source. Data were collected with this instrument using a modified version of the rapid-scanning method. A prerequisite in employing the rapid-scan detection scheme is that the modulation used to scan the laser be synchronized in time with the electrical signal used to trigger the pulsed gas valve. Software performance was evaluated by examining a series of rotation vibration (ro-vibrational) spectra for the carbon monoxide molecule in the five micron region of the infrared

Infrared Diode Laser Spectrometer for the Study of Jet Cooled Gases

We have constructed a tunable, high resolution, infrared diode laser spectrometer and combined it with a pulsed supersonic jet expansion. A modified version of the Perry multipass cell has been incorporated into the spectrometer to increase the effective absorption path length. Performance capabilities of the spectrometer are evaluated by examining ro-vibrational spectra for the carbon monoxide molecule in the five micron region of the infrared. From these measurements, an instrumental absorption sensitivity is determined. Finally, since one of our immediate goals is the infrared study of jet cooled transition metal carbonyls, we present high resolution data obtained by entraining the vapor above a solid metal carbonyl and injecting it into the pulsed jet expansion

Investigations into the DNP characteristics of electron and proton irradiated polyethylene and polypropylene

To achieve a significant enhancement of the nuclear polarisation of solid state target materials one must use the method of dynamic nuclear polarisation. This necessitates unpaired electrons, that can be created as paramagnetic structural defects by the irradiation of materials. To this end polyethylene (PE) and polypropylene (PP) materials were irradiated by 13MeV protons at a temperature of 120K and over a temperature range of 87K to 210K with ~20MeV electrons. The identification of the radical types that are created, as well as the quantification of the unpaired electron density, was made in a conventional ESR spectrometer. Samples were polarised in a 2.5 T magnetic field at a temperature of 1 K. It was found that the irradiation temperature has an effect on the nuclear relaxation times of the materials. Higher irradiation temperatures result in lower radical yields and consequently longer relaxation times. Both materials exhibit an increase of polarisation values for an increase in irradiation temperature. The largest polarisation values were obtained in the PE materials of around 20% when irradiated at a temperature of 210 K, but PP only reached a maximum of 8% at the same irradiation temperature. Better results for the PP materials, in terms of polarisation values, were obtained by the heating of the samples at room temperature post irradiation. Here it was possible to obtain results of 14% polarisation

Spectroscopic Temperature Measurements for a Direct Current Arcjet Diamond Chemical Vapor Deposition Reactor

The diamond thin filmcommercial market isprojected to exceed one billion dollars by the year 2000. Potential applications of diamond thin films range from cutting tools to electronics tomedical devices. The explosion ofinterest in this fieldresults from the extreme properties diamond possesses: itis the hardest material known toman and yet, has a coefficient of friction similar to Teflon;its ability to conduct heat is five times that of copper; and diamond is completely inert. However, despite the tremendous economic incentive, there are still several technological barriers preventing diamond filmscale-up to commercial production. Included among these are a fundamental understanding of the gas phase chemistry leading to diamond filmformation and the lack of a reliable insitu, on-line Chemical Vapor Deposition (CVD)monitoring capability. Here we describe the use of optical emission spectroscopy (OES) as a possible direct current CVD plasma jet on-line monitor. Specifically, OES spectra from the C2 radical, an intermediate species in the diamond CVD process, is utilized to obtain plasma gas temperatures insitu. Additionally, the reliability of a plasma gas temperature determined fromOES is examined withLaser-Induced-Fluorescence (LIF)

Multi-Color Cavity Ringdown Based Detection Method and Apparatus

A multi-color cavity ringdown based spectrometer system is housed in a light tight enclosure to detect the presence of trace quantities of gas phase molecules emanating from a subject, explosives, drugs, or hazardous materials. A method is also disclosed for simultaneous real time detection of gas phase molecules emanating from explosives, drugs, hazardous materials, a subject\u27s breath skin or bodily fluid

The Desired Characteristics of Hospitality/Tourism Management Employees: A Review of Research Quality

Numerous studies have sought to measure the characteristics most desired by employers of hospitality and tourism management graduates. For the results of these studies to be meaningful, they need to conform to generally accepted principles of science. While there is no a priori reason to suggest that the research is flawed in any meaningful way, a preliminary examination can nonetheless confirm the level of research quality and help identify any limitations. The purpose of this study, therefore, is to examine the quality of the research evidence with particular attention to: (1) the characteristics selected for measurement, (2) the measurement techniques used, (3) the characteristics of the sample, and (4) the reporting of results. The results indicate limitations in each area. Recommendations for addressing these in future research are discussed