Matching Items (6)

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Detection and characterization of singly deuterated silylene, SiHD, via optical spectroscopy

Description

Singly deuterated silylene has been detected and characterized in the gas-phase using high-resolution, two-dimensional, optical spectroscopy. Rotationally resolved lines in the 0[0 over 0][˜ over X][superscript 1]A′ → [˜ over

Singly deuterated silylene has been detected and characterized in the gas-phase using high-resolution, two-dimensional, optical spectroscopy. Rotationally resolved lines in the 0[0 over 0][˜ over X][superscript 1]A′ → [˜ over A][superscript 1]A′′000X˜1A′→A˜1A″ band are assigned to both c-type perpendicular transition and additional parallel, axis-switching induced bands. The extracted rotational constants were combined with those for SiH[subscript 2] and SiD[subscript 2] to determine an improved equilibrium bond length, r[subscript SiH], and bond angle, θ, of 1.5137 ± 0.0003 Å and 92.04° ± 0.05°, and 1.4853 ± 0.0005 Å and 122.48° ± 0.08° for the [˜ over X][superscript 1]A′(0, 0, 0) and [˜ over A][superscript 1]A″(0, 0, 0) state respectively. The dispersed fluorescence consists of a long progression in the [˜ over A][superscript 1]A″(0,0,0) → [˜ over X][superscript 1]A′(0, ν[subscript 2], 0) emission which was analyzed to produce vibrational parameters. A strong quantum level dependence of the rotationally resolved radiative decay curves is analyzed.

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Date Created
  • 2016-06-27

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Synthesis and Characterization of Laser Plasma that Produces Pseudocarbyne Using Laser Pulses

Description

Carbon allotropes are the basis for many exciting advancements in technology. While sp² and sp³ hybridizations are well understood, the sp¹ hybridized carbon has been elusive. However, with recent advances

Carbon allotropes are the basis for many exciting advancements in technology. While sp² and sp³ hybridizations are well understood, the sp¹ hybridized carbon has been elusive. However, with recent advances made using a pulsed laser ablation in liquid technique, sp¹ hybridized carbon allotropes have been created. The fabricated carbon chain is composed of sp¹ and sp³ hybridized bonds, but it also incorporates nanoparticles such as gold or possibly silver to stabilize the chain. The polyyne generated in this process is called pseudocarbyne due to its striking resemblance to the theoretical carbyne. The formation of these carbon chains is yet to be fully understood, but significant progress has been made in determining the temperature of the plasma in which the pseudocarbyne is formed. When a 532 nm pulsed laser with a pulsed energy of 250 mJ and pulse length of 10ns is used to ablate a gold target, a peak temperature of 13400 K is measured. When measured using Laser-Induced Breakdown spectroscopy (LIBS) the average temperature of the neutral carbon plasma over one second was 4590±172 K. This temperature strongly suggests that the current theoretical model used to describe the temperature at which pseudocarbyne generates is accurate.

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Date Created
  • 2019-05

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Designing of a Dynamic Liquid Z-Scan Spectrometer

Description

This paper outlines the design and testing of a z-scan spectrometer capable of measuring the third order refraction index of liquids. The spectrometer underwent multiple redesigns, with each explored

This paper outlines the design and testing of a z-scan spectrometer capable of measuring the third order refraction index of liquids. The spectrometer underwent multiple redesigns, with each explored in this paper with their benefits and drawbacks discussed. The first design was capable of measuring the third order refraction index for glass, and found a value of 8.43 +- 0.392 x 10^(-16) cm^2/W for the glass sample, with the literature stating glass has a refraction index between 1-100 x 10^(-16) cm^2/W. The second design was capable of measuring the third order refraction index of liquids, and found values of 1.23 $\pm$ 0.121 $\e{-16}$ and 9.43 +- 1.00 x 10^(-17) cm^2/W for water and ethanol respectively, with literature values of 2.7 x 10^(-16) and 5.0 x 10^(-17) cm^2/W respectively. The third design gave inconclusive results due to extreme variability in testing, and and the fourth design outlined has not been tested yet due to time constraints.

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Date Created
  • 2021-05

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Unique High Fire Glaze Development

Description

Experimentation with glaze materials resulted in 2 functional and interesting base glazes with multiple color variants each. A semi-matte stoneware glaze was created, however after being unable to replicate a

Experimentation with glaze materials resulted in 2 functional and interesting base glazes with multiple color variants each. A semi-matte stoneware glaze was created, however after being unable to replicate a specific coloring without drying out the glaze, it was discovered that using this glaze to spray over specific studio glazes produced a more pleasant color effect than the glaze by itself. A glossy clear glaze was created. The glaze crazed minimally, and color variants were created with the rare earth metals erbium, praseodymium, and neodymium, resulting in celadon-like glazes that were pink, green, and bluish purple respectively. Finally, A semi-matte stoneware glaze with high spodumene content was created with two specific color variations

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Date Created
  • 2019-05

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High pressure and high temperature study on lithium carbide (Li₂C₂) and calcium carbide (CaC₂): an attempt to make a novel polyanionic form of carbon

Description

Carbon lacks an extended polyanionic chemistry which appears restricted to carbides with C4-, C22-, and C34- moieties. The most common dimeric anion of carbon atoms is C22- with a triple

Carbon lacks an extended polyanionic chemistry which appears restricted to carbides with C4-, C22-, and C34- moieties. The most common dimeric anion of carbon atoms is C22- with a triple bond between the two carbon atoms. Compounds containing the dicarbide anion can be regarded as salts of acetylene C2H2 (ethyne) and hence are also called acetylides or ethynides. Inspired by the fact that molecular acetylene undergoes pressure induced polymerization to polyacetylene above 3.5 GPa, it is of particular interest to study the effect of pressure on the crystal structures of acetylides as well. In this work, pressure induced polymerization was attempted with two simple metal acetylides, Li2C2 and CaC2. Li2C2 and CaC2 have been synthesized by a direct reaction of the elements at 800ºC and 1200ºC, respectively. Initial high pressure investigations were performed inside Diamond anvil cell (DAC) at room temperature and in situ Raman spectroscopic measurement were carried out up to 30 GPa. Near 15 GPa, Li2C2 undergoes a transition into a high pressure acetylide phase and around 25 GPa this phase turns amorphous. CaC2 is polymorphic at ambient pressure. Monoclinic CaC2-II does not show stability at pressures above 1 GPa. Tetragonal CaC2-I is stable up to at least 12 GPa above which possibly a pressure-induced distortion occurs. At around 18 GPa, CaC2 turns amorphous. In a subsequent series of experiments both Li2C2 and CaC2 were compressed to 10 GPa in a multi anvil (MA) device and heated to temperatures between 300 and 1100oC for Li2C2, and 300°C to 900°C for CaC2. The recovered products were analyzed by PXRD and Raman spectroscopy. It has been observed that reactions at temperature higher than 900°C were very difficult to control and hitherto only short reaction times could be applied. For Li2C2, a new phase, free of starting material was found at 1100°C. Both the PXRD patterns and Raman spectra of products at 1100oC could not be matched to known forms of carbon or carbides. For CaC2 new reflections in PXRD were visible at 900ºC with the starting material phase.

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Date Created
  • 2012

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Dielectric response of glass-forming liquids in the nonlinear regime

Description

Broadband dielectric spectroscopy is a powerful technique for understanding the dynamics in supercooled liquids. It generates information about the timescale of the orientational motions of molecular dipoles within the liquid.

Broadband dielectric spectroscopy is a powerful technique for understanding the dynamics in supercooled liquids. It generates information about the timescale of the orientational motions of molecular dipoles within the liquid. However, dynamics of liquids measured in the non-linear response regime has recently become an area of significant interest, because additional information can be obtained compared with linear response measurements.

The first part of this thesis describes nonlinear dielectric relaxation experiments performed on various molecular glass forming-liquids, with an emphasis on the response at high frequencies (excess wing). A significant nonlinear dielectric effect (NDE) was found to persist in these modes, and the magnitude of this NDE traces the temperature dependence of the activation energy. A time resolved measurement technique monitoring the dielectric loss revealed that for the steady state NDE to develop it would take a very large number of high amplitude alternating current (ac) field cycles. High frequency modes were found to be ‘slaved’ to the average structural relaxation time, contrary to the standard picture of heterogeneity. Nonlinear measurements were also performed on the Johari-Goldstein β-relaxation process. High ac fields were found to modify the amplitudes of these secondary modes. The nonlinear features of this secondary process are reminiscent of those found for the excess wing regime, suggesting that these two contributions to dynamics have common origins.

The second part of this thesis describes the nonlinear effects observed from the application of high direct current (dc) bias fields superposed with a small amplitude sinusoidal ac field. For several molecular glass formers, the application of a dc field was found to slow down the system via reduction in configurational entropy (Adam-Gibbs relation). Time resolved measurements indicated that the rise of the non-linear effect is slower than its decay, as observed in the electro-optical Kerr effect. A model was discussed which quantitatively captures the observed magnitudes and time dependencies of the NDE. Asymmetry in these rise and decay times was demonstrated as a consequence of the quadratic field dependence of the entropy change. It was demonstrated that the high bias field modifies the polarization response to the field, even including the zero field limit.

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Date Created
  • 2016