The development of a combustion temperature standard for the calibration of optical diagnostic techniques

This thesis describes the development and evaluation of a high-temperature combustion standard. This comprises a McKenna burner premixed flame, together with a full assessment of its temperature, stability and reproducibility. I have evaluated three techniques for high-accuracy flame thermometry: Modulated Emission in Gases (MEG), Rayleigh scattering thermometry and photo-acoustic thermometry. MEG: Analysis shows that MEG is not usable in this application because the sharp spectral features of the absorption coefficient of gases are represented within MEG theory as an average absorption coefficient over the optical detection bandwidth. A secondary difficulty arises from the lack of high power lasers operating at wavelengths that coincides with molecular absorption lines in the hot gas. Rayleigh Scattering: Applying corrections for the temperature-dependence of the scattering cross-section, it has been possible to determine the temperature of the combustion standard with an uncertainty of approximately 1%. The temperature dependence of the scattering cross-section arises from changes in the mean molecular polarisability and anisotropy and can amount to 2% between flame and room temperatures. Using a pulse Nd-YAG laser operating at 532 nm and high linearity silicon detectors, the Rayleigh scattering experimental system has been optimised. Temperatures measured over a three-month interval are shown to be reproducible to better than 0.4% demonstrating the suitability of the McKenna burner as a combustion standard. Photo-Acoustic: By measuring the transit time of a spark-induced sound wave past two parallel probe beams, the temperature has been determined with an uncertainty of approximate 1%. Flame temperatures measured by the photo-acoustic and Rayleigh scattering thermometry system show good agreement. For high airflow rates the agreement is better than 1% of temperature, but for low airflow rates, photo-acoustic temperatures are approximately 3.6% higher than the Rayleigh temperatures. Further work is needed to understand this discrepancy

The development of a combustion temperature standard for the calibration of optical diagnostic techniques

This thesis describes the development and evaluation of a high-temperature combustion standard. This comprises a McKenna burner premixed flame, together with a full assessment of its temperature, stability and reproducibility. I have evaluated three techniques for high-accuracy flame thermometry: Modulated Emission in Gases (MEG), Rayleigh scattering thermometry and photo-acoustic thermometry. MEG: Analysis shows that MEG is not usable in this application because the sharp spectral features of the absorption coefficient of gases are represented within MEG theory as an average absorption coefficient over the optical detection bandwidth. A secondary difficulty arises from the lack of high power lasers operating at wavelengths that coincides with molecular absorption lines in the hot gas. Rayleigh Scattering: Applying corrections for the temperature-dependence of the scattering cross-section, it has been possible to determine the temperature of the combustion standard with an uncertainty of approximately 1%. The temperature dependence of the scattering cross-section arises from changes in the mean molecular polarisability and anisotropy and can amount to 2% between flame and room temperatures. Using a pulse Nd-YAG laser operating at 532 nm and high linearity silicon detectors, the Rayleigh scattering experimental system has been optimised. Temperatures measured over a three-month interval are shown to be reproducible to better than 0.4% demonstrating the suitability of the McKenna burner as a combustion standard. Photo-Acoustic: By measuring the transit time of a spark-induced sound wave past two parallel probe beams, the temperature has been determined with an uncertainty of approximate 1%. Flame temperatures measured by the photo-acoustic and Rayleigh scattering thermometry system show good agreement. For high airflow rates the agreement is better than 1% of temperature, but for low airflow rates, photo-acoustic temperatures are approximately 3.6% higher than the Rayleigh temperatures. Further work is needed to understand this discrepancy.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Dynamics of interfering wave packets in rubidium by high resolution quantum beat spectroscopy

High resolution quantum beat spectroscopy has been realized to study atomic wave packet dynamics. Wave packets comprising pairs of low quantum number (n = 5 - 8) electronic states were formed in Rb vapor with ultrafast laser pulses, and their dynamics was observed by an all-optical technique of parametric four wave mixing (PFWM). The experimental apparatus designed, constructed and automated for this work provided unprecedented signal intensity that enabled time-frequency-resolved analysis of wave packet dynamics with picosecond temporal resolution over the course of 1100 ps. Both time-resolved and non-time-resolved discrete Fourier methods were applied to measure the concurrent formation of multiple wave packets. Many novel effects and interactions have been measured either for the first time or with greatly improved signal-to-noise ratio. Among them were the formation of the 8S1/2 - 6D5/2 wave packet that was not directly excited by the ultrafast radiation, formation and relative dynamics of quantum beating harmonics up to 73 THz, and quantum beating revivals. The effects of vapor number density and temperature were analyzed experimentally. Interference between the 7S1/2 - 5D5/2 and 8S1/2 - 6D5/2 wave packets (frequencies of 18.225 THz and 10.73 THz, respectively) has been observed for the first time and will be described in detail

Ultrafast structural dynamics in electronically excited many-body systems

This thesis reports on results of three different experiments of photo-induced structural dynamics in the condensed phase, investigated by time-resolved pump-probe spectroscopy with femtosecond time-resolution. In the first part, we address the ultrafast dynamics of a quantum solid : crystalline hydrogen. This is accomplished by optical excitation of a dopant molecule, Nitric Oxide (NO), to a large orbital Rydberg state, which leads to a bubble-like expansion of the species surrounding the impurity. The dynamics is directly inferred from the time-resolved data, and compared with the results of molecular dynamics simulations. We report the presence of three time-scales in the structural relaxation mechanism: the first 200 fs are associated with the ultrafast inertial expansion of the first shell of lattice neighbors of NO. During the successive 0.6 ps, as the interactions between the molecules of the first and of the successive shells increase, we observe a progressive slowing-down of the bubble expansion. The third timescale (~ 10 ps) is interpreted as a slow structural re-organization around the impurity center. No differences were observed between the dynamics of normal- and para-hydrogen crystals, justifying the simplified model we use to interpret the data, which ignores all internal degrees of freedom of the host molecules. The molecular dynamics simulations reproduce fairly well the static and dynamic features of the experiment. In line with the measurements, they indicate that the quantum nature of the host medium plays no role in the initial ultrafast expansion of the bubble. In the second part, we present the results of our study on the photo-physics of triangular-shaped silver nanoparticles upon intraband excitation of the conduction electrons. The picosecond dynamics is dominated by periodic shifts of the surface plasmon resonance, associated with the size oscillations of the particles, triggered by impulsive lattice heating by the laser pulse. The oscillation period compares very well with the lowest totally symmetric vibrational frequency of a triangular-plate, which we calculated improving an existing elastodynamic model. We propose an explanation for the unusual phase behavior of the oscillations, based upon the non-spherical shape, and size-inhomogeneity of the sample. Taking into account these effects, we are able to reproduce spectrally and temporally our data. In the last part, we present a comparative study of the ligand dynamics in heme proteins. We studied the photo-induced spectroscopic changes in the ferric CN complexes of Myoglobin and Hemoglobin I upon photo-excitation of the porphyrin ring to a low-lying electronic state (Soret), monitoring the UV-visible region of the Soret band, and the mid-infrared region of the fundamental C=N vibrational stretch. The transient response in the UV-visible spectral region does not depend on the heme pocket environment, and is very similar to that known for ferrous proteins. The infrared data on the MbC=N stretch vibration provides a direct measure for the return of population to the ligated electronic (and vibrational) ground state with a 3 ps time constant. In addition, the CN stretch frequency is sensitive to the excitation of low frequency heme modes, and yields independent information about vibrational cooling, which occurs on the same timescale. The similarity between ferrous and ferric hemes rules out the charge transfer processes commonly invoked to explain the ligand dissociation in the former

Picosecond X-ray absorption spectroscopy:application to coordination chemistry compounds in solution

The photocycle of aqueous ruthenium-(trisbipyridine) [Ru(bpy)3]2+ was studied under high laser excitation intensities and high sample concentrations with picosecond resolved x-ray absorption spectroscopy. In a pump-probe scheme a femtosecond laser pulse promotes a 4d electron from the ruthenium to the ligand orbitals, thus creating a metal-to-ligand-charge-transfer (MLCT) complex. A hard x-ray pulse from a synchrotron source probes the ruthenium L3 and L2 edges, monitoring the electronic and molecular structure of the ruthenium over the photocycle. The measured x-ray absorption spectrum of the MLCT state is in good agreement with the predictions of a theoretical calculation (TT-multiplet software). We extract from the spectrum that the excited-state complex can be described by D3 symmetry and has a 4d5 configuration. The decay kinetics of the MLCT state are found to be strongly dependent on the sample concentration, especially for solutions near the solubility limit of [Ru(bpy)3]Cl2 in water. Besides ground-state quenching and triplet-triplet annihilation a third fast decay component quenches the life-time of the MLCT state, tentatively attributed to a cluster effect. This study is the first application of sub-nanosecond time-resolved x-ray absorption spectroscopy on solvated systems and demonstrates its capability as a new tool for the observation of chemical dynamics in solvated systems

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本文データは平成22年度国立国会図書館の学位論文(博士)のデジタル化実施により作成された画像ファイルを基にpdf変換したものである京都大学0048新制・課程博士博士(工学)甲第8524号工博第1978号新制||工||1186(附属図書館)UT51-2000-J33京都大学大学院工学研究科分子工学専攻(主査)教授 川﨑 昌博, 教授 横尾 俊信, 教授 中辻 博学位規則第4条第1項該当Doctor of EngineeringKyoto UniversityDFA

Probing transient species in plasmas and photodissociation reactions using infrared and raman laser spectroscopy

Ph.DDOCTOR OF PHILOSOPH