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Frequency-swept rapid-scan EPR on organic radicals
Tuček, Marek ; Marko, Andriy (oponent) ; Neugebauer, Petr (vedoucí práce)
This thesis describes a historically first multi-frequency rapid-scan EPR. While introducing microwave radiation at 200 GHz range with subsequent sinusoidal modulation, the frequency sweep rates up to 61 500 THz/s were achieved and the rapid passage distortion known as ”wiggles” was observed in the spectra of both studied organic radicals samples – BDPA in a polystyrene matrix and LiPc. This thesis presents a flexible method of conducting rapid-scan EPR experiments, using a voltage controlled oscillator (VCO) and zero-bias detector (ZBD) as a source and detector, respectively, and thus opening the possibility to advance further into high field / high frequency range. Furthermore, the method of extracting the steady-state absorption spectra from the rapid-scan results, known as Fourier deconvolution, is described and subsequently, the spin dephasing times of the samples are determined from the comparison of the spectra with the results of numerically solved Bloch equations. The resulting values are 50 ns for BDPA and 12 ns for LiPc.
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Frequency-swept rapid-scan EPR on organic radicals
Tuček, Marek ; Marko, Andriy (oponent) ; Neugebauer, Petr (vedoucí práce)
This thesis describes a historically first multi-frequency rapid-scan EPR. While introducing microwave radiation at 200 GHz range with subsequent sinusoidal modulation, the frequency sweep rates up to 61 500 THz/s were achieved and the rapid passage distortion known as ”wiggles” was observed in the spectra of both studied organic radicals samples – BDPA in a polystyrene matrix and LiPc. This thesis presents a flexible method of conducting rapid-scan EPR experiments, using a voltage controlled oscillator (VCO) and zero-bias detector (ZBD) as a source and detector, respectively, and thus opening the possibility to advance further into high field / high frequency range. Furthermore, the method of extracting the steady-state absorption spectra from the rapid-scan results, known as Fourier deconvolution, is described and subsequently, the spin dephasing times of the samples are determined from the comparison of the spectra with the results of numerically solved Bloch equations. The resulting values are 50 ns for BDPA and 12 ns for LiPc.
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