Robert R. Reeves

Mixed solvent systems for optimizing output from a pulsed dye laser

Abstract The output intensity from a N2 laser pumped dye laser has been optimized at 507 nm by the use of a mixture of solvents with a single dye. The wavelength of maximum output power of coumarin 481 was found to depend on the composition of the solvent mixture. With coumarin 481 in a 2: 1 volume mixture of p-dioxane and ethanol, a maximum power output was obtained at 507 nm, versus 481 nm for the same dye in pure p-dioxane or 517 nm for the same dye in pure ethanol, A 3 : 1 volume mixture of p-dioxane and ethanol and a 1 : 1 mixture gave lasing maxima at 501 nm and 511 nm, respectively. The energy per pulse at 507 nm obtained with coumarin 481 in the 2 : 1 mixture was compared with the energy per pulse obtained with coumarin 481 in pure p-dioxane and with the energy per pulse obtained with coumarin 540A in both high resolution. The relative photochemical stabilities of cuomarin 481 in the 2 : 1 mixture, coumarin 481 in pure p-dioxane and coumarin 540A in pure p-dioxane are also evaluated.

CVD of copper using copper(I) and copper(II) β-diketonates

Abstract Reaction paths for the chemical vapor deposition (CVD) of copper from (hfac)Cu(vtms), Cu(hfac) 2 , and Cu(fod) 2 were studied using mass spectrometric analysis of the reaction products. Cu(hfac) 2 was identified as one of the products when (hfac)Cu(vtms) reacts with or without hydrogen at temperatures from 130 to 235 °C in a hot-wall batch reactor. Therefore, the route to copper formation is a disproportionation reaction which we found to be reversible under all operating conditions. The reverse reaction regenerates the precursor, (hfac)Cu(vtms). Our experiments show that Cu(hfac) 2 reacts very slowly with H 2 at temperatures below 250 °C, which typically are used for (hfac)Cu(vtms). Therefore, below 250 °C, the deposition rate of copper from (hfac)Cu(vtms) is not increased by the reaction of its product, Cu(hfac) 2 , with hydrogen. For CVD using Cu(hfac) 2 and Cu(fod) 2 with hydrogen, Hhfac and Hfod are the reaction products.

Reaction of Oxygen Atoms with Nitric Oxide

The rate of reaction of oxygen atoms with nitric oxide has been studied at several pressures (0.62, 0.85, 1.11 mm Hg) by measuring the relative intensities of the oxygen afterglow. The consumption of O atoms was observed as a three‐body recombination (NO+O+M→NO2+M). At room temperature the reaction coefficient was found to be k2=7.6×10‐32 cm6 molecules‐2 sec‐1, with an average deviation of 6.5%. The third body was mainly argon.

Chemiluminescent Nitric Oxide—Oxygen‐Atom Reaction at Low Pressures

The light emitting reaction NO+O→NO2+hv is shown to be second order in the pressure region of 3 to 20 μ. This would indicate that the major source of emission is a simple radiative combination of nitric oxide and oxygen atoms. In addition, any excitation and emission mechanism involving a third body would be too small to account for the light emission observed.

Determination of the lifetime of the mercury 63P1 state

Abstract A pulsed tunable dye laser was used for a high resolution experimental study of mercury fluorescence from the 6 3 P 1 state. The output of the dye laser was frequency doubled into the 253.7 nm region using a potassium penta-borate crystal. Exponential decays were observed for each of the five individual components of the hyperfine structure separately and the effects of the trapping of resonance radiation on the observed lifetime of the 6 3 P 1 state of mercury were investigated for each resolvable component. Within experimental error, the natural radiative lifetime of the 6 3 P 1 state was found to be independent of the hyperfine component irradiated and a value of 122±2 nsec was obtained, consistent with results found by other methods.

Tungsten film deposition by hydrogen atom reaction with WF6

The formation of tungsten films using WF6 and molecular hydrogen, H2, usually requires elevated temperatures. Using the reaction of hydrogen atoms with WF6, tungsten atoms can be produced in a gas phase reaction. The atoms then deposit in a near‐room temperature process resulting in the formation of tungsten films. The W atoms were measured in situ by atomic absorption spectroscopy during the chemical vapor deposition (CVD) process. The deposited W films were characterized by Auger electron spectroscopy and Rutherford backscattering spectrometry. Surface morphology of the films was studied using scanning electron microscopy. The deposited films were highly adherent to various substrates, including Teflon. The resistivity of the W films was measured and found ≥9 μΩ cm. This method allows deposition of high quality films and has two advantages compared to conventional CVD or plasma‐enhanced CVD (PECVD): (1) film growth at low temperatures and (2) deposition in a plasma‐free environment.

The role of phosphorus in the upper atmosphere of Jupiter

Abstract The reaction of elemental phosphorus and H atoms to form PH3 was observed and should be a major factor in the recycling of PH3 in the stratosphere of Jupiter. The formation of PH3 in this manner should predominate at high altitudes where, due to the very low temperatures, reactions that require higher activation energies than these atom reactions cannot occur. At lower altitudes, in the troposphere, the rapid formation of H atoms from the strong absorption of light by NH3 will contribute to phosphine production also in this same manner. Recent experiments have also shown that elemental phosphorus reacts readily with aqueous ammonia to form PH3. This reaction may also be important in the recycling of PH3 in the upper troposphere of Jupiter if water-ammonia clouds, as had been previously thought, exist. Considerations of the coloration of the Great Red Spot have been made based upon the nature of the phosphorus obtained by decomposition of phosphine.

Dust injection into the Martian atmosphere

Abstract A mechanism for initiating global dust storms on Mars is proposed in which the diurnal variation of surface temperature results in the desorption of adsorbed CO 2 , which under certain conditions can inject large amounts of fine (1–10 μm) dust into the atmosphere.

The chemiluminescent NO - O-atom reaction.

Abstract— New additional experimental data were obtained to give further information pertinent to the mechanism for the chemiluminescent NO—O‐atom reaction. Results were obtained for the change of emission intensities from 10 to 300 microns pressure. Some studies were also made of the effect of various third bodies. The results support a simple two body recombination for the mechanism for the light emission: NO+O + NO2+hv.

The Iodine Lamp: A Light Source for Selective Excitation of CO

A light source has been developed for photochemical studies which emits the 2062 A line of iodine. This lamp has been used to study reactions of CO excited in the a 3Π level. Carbon monoxide was irradiated in an experimental lamp incorporating an arrangement of concentric cylinders. The output of this lamp was 2 · 1018 quanta per second. The CO a3Π molecules react to form CO2 with a quantum efficiency between a few tenths and unity.