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Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 34 for “"rovibrational"”.
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Rovibrational Dynamics of Nuclei and Molecules
We study quantized rotation-vibration dynamics with applications to nuclear and molecular models. Firstly we consider small vibrations of Skyrmions (topological solitons which model atomic nuclei), developing new approximations to their quantum energy spectra which incor- porate both …
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Infrared Studies of Intramolecular Rovibrational Relaxation (Kinetics, Energy Transfer)
… statistical model which assumes coupling to all rovibrational states of the correct symmetry within 1 cm('-1) of the excitation frequency. The comparison of the relaxation in beams with rotational temperatures of 2 and 20 K demonstrates the extent of the rotational dependence of the IVR. It is …
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Rovibrational State Mixing in Isolated Ground Electronic State Polyatomic Molecules
Rovibrational state mixing in ground electronic state polyatomic molecules has been studied using infrared laser induced fluorescence and stimulated emission pumping (SEP) spectroscopy. Molecules are cooled and isolated in supersonic molecular beams. A relationship between state mixing, measured as …
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Product Basis Set Variational Calculations of Triatomic Rovibrational Energy Levels and Wavefunctions
If both the potential energy surface of a molecule and trial functions for a variational calculation are expanded in products of internal coordinate functions, the Hamiltonian matrix may be speedily built because all required integrals are one-dimensional. New methods, especially for calculating …
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High-resolution spectroscopic investigations of rovibrational state mixing in ground electronic states
High resolution spectroscopic studies of rovibrational state mixing in the ground electronic state of the molecules methyl glyoxal and methyl formate are presented. The technique of Stimulated Emission Pumping (SEP) spectroscopy is used to examine the effect of an intramolecular van der Waals …
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Sensitive and high-precision rovibrational spectroscopy of molecular ions relevant to astronomical and quantum chemistry
… laboratory measurements of rotational and rovibrational transition frequencies, which is particularly challenging for molecular ions. This is because ions are generated in small quantities within laboratory discharges, which are easily obscured by the far more abundant neutral molecules. …
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An ultracold gas of dipolar fermionic ²³Na⁴⁰K molecules
… dipolar molecules of ²³Na⁴⁰K in the singlet rovibrational ground state. These fermionic molecules have a large permanent electric dipole moment of 2.72 Debye, and are chemically stable against inelastic dimer-dimer reactions. A quantum gas of these molecules have potential applications in …
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Development of a high-fidelity thermochemical model for the O2+O system using direct simulation Monte Carlo
… done with three aspects for DSMC: (i) develop a rovibrationally resolved state-to-state model for energy transfer, dissociation and recombination reactions; (ii) investigate the coarse-grain models to improve the expensive computational cost of the state-to-state model; (iii) examine the …
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Spectroscopy and theory of cis-trans isomerization in the S₁ state of acetylene
… experimental and theoretical studies of the rovibrational structure and dynamics of the Si state of acetylene, C2H2 . This small molecule is a prototypical system for the study of cis-trans isomerization, the barrier to which is moderately low in the Si state, presenting the opportunity to …
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High-resolution spectroscopic studies of carbon-containing species
… From the fundamental side, high-resolution rovibrational spectroscopy allows molecular constants to be determined and provides evidence of theoretical assumptions. Work to this end was performed using cavity-ringdown spectroscopy and either a gas phase or supercritical fluid supersonic …
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Ultrafast Dynamics and Nonlinear Interactions in Alkali Atoms and Diatomics
… techniques have been used to study the rovibrational dynamics of the B, C, and D states of the Cesium dimer and to study atomic wavepackets and nonlinear effects in Rubidium and Potassium. Two color, pump-probe techniques have been used to probe the time evolution of wavepackets in the …
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Machine learning and uncertainty quantification framework for predictive ab initio Hypersonics
… This study is done at both microscopic (e.g., rovibrational-specific rate coefficients) and macroscopic (e.g., thermal and chemical relaxation properties) levels. A correlation analysis is finally applied to identify the PES regions that require further refinement, based on their effects on the …
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Maximum entropy quadratic model to characterize chemical non-equilibrium in re-entry flows
… of moments. The focus of this project is on the rovibrational chemical kinetics of the N2-N system. Internal excitation, dissociation, recombination and energy transfer reactions, which are important processes in aerothermodynamics, are studied. The kinetic and thermodynamic data is obtained from …
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Internal Excitations of Stored Triatomic Hydrogen Molecular Ions
… (12000 K) after more than 10s. A comprehensive rovibrational excitation model, based on theoretical calculations of transition probabilities can explain the experimental observations. For future experiments, a cryogenic 22-pole ion trap was constructed, which is capable of preparing …
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Quantum State Singlet-Triplet Character Control in 7Li2
… energy levels of interest are two closely spaced rovibrational levels (the G1Πg (12, 21f) and 13Sg- (1, 21f) states separated by 720 MHz). In the absence of any optical fields, the spin-orbit interaction couples the two states, resulting in each state being a mixture of the pure singlet and pure …
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Reduced-order model framework for thermochemical non-equilibrium hypersonic flows
… and one which relies on the assumption of strong rovibrational coupling. In a study of the isothermal relaxation of nitrogen molecules, it is found using these two approaches that the underlying assumptions made in conventional chemical non-equilibrium models (i.e., that vibrational and rotational …
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Development of a sensitive mid-infrared spectrometer for the study of cooled molecular ions
… has been developed and characterized through rovibrational spectroscopy of methane. In addition, an attempt was made to use this spectrometer to probe molecular ions focused into an ion beam. Challenges inherent to laboratory molecular ion spectroscopy, such as quantum dilution at high …
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LiNaK : multi-species apparatus for the study of ultracold quantum degenerate mixtures
… Feshbach molecules of NaK into the singlet rovibrational ground state.
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The spectroscopy of bound and predissociating Rydberg states of NO in external electric fields
… excitation via the υ′ = 0,N′ = 0, 1, 2, and 4 rovibrational states of the A2Σ+ state. The N (2D) atoms produced by predissociation are measured by (2 + 1) resonance-enhanced multiphoton ionization. The zero field and predissociation spectra are analysed using a matrix diagonalisation method. In …
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An experimental study and modeling of Transformer-Coupled Toroidal Plasma processing of materials
… of plasma-surface interactions. By fitting the rovibrational bands of diatomic molecules such as N2, the temperatures of neutral gases were determined in the TCTP source. This was the first measurement of the neutral gas temperature of a high power density plasma in a toroidal geometry. An argon …
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