18 research outputs found
Stimulated Raman gain spectra measured by a cavity-ringdown technique
No full textWe report a novel form of high-resolution coherent-Raman spectroscopy which detects stimulated Raman gain effects using a cavity-ringdown technique. This is demonstrated by recording molecular rovibrational Raman spectra of methane gasFlorian V. Englich, Yabai He, and Brian J. Or
Continuous-wave cavity-ringdown detection of stimulated Raman gain spectra
No full textCavity ringdown (CRD) spectroscopy, with its high sensitivity, provides a novel way to perform continuous-wave (cw) stimulated Raman gain (SRG) spectroscopy, rather than by conventional optically detected coherent Raman techniques. Tunable cw laser light at ∼ 1544 nm is used to probe ringdown decay from a rapidly-swept, high-finesse optical cavity containing a gas-phase sample of interest and itself located inside the cavity of a cw single-longitudinal-mode Nd:YAG ring laser operating at ∼ 1064.4 nm. This approach is used to measure cw SRG spectra of the ν 1 fundamental rovibrational Raman band of methane gas at ∼ 2916.5 cm-1. The resulting SRG-CRD resonances have ringdown times longer than in the off-resonance case, in contrast to the usual shorter ringdown times arising from absorption and other loss processes. Previously reported noise-equivalent sensitivities have been substantially improved, by using a second ringdown cavity to facilitate subtraction of infrared-absorption background signals. Moreover, by employing a ringdown cavity in the form of a ring, the SRG-pump and CRD-detected Stokes beams can co-propagate uni-directionally, which significantly reduces Doppler broadening. © 2008 Springer-Verlag.F.V. Englich, Y. He and B.J. Or
Multi-wavelength, rapidly swept continuous-wave cavity ringdown spectroscopy, applied to sensing of greenhouse gases
No full textThe greenhouse gas molecules CH4, CO2, and H 2O are detected by using a cavity ringdown laser spectrometer with rapidly swept optical cavity and multi-wavelength coherent radiation. This sensitive portable instrument is applicable to environmental monitoring. ©2009 Optical Society of America.Yabai He, Ruifeng Kan, Florian V. Englich, Wenqing Liu and Brian J. Or
Photoinduced electron transfer based ion sensing within an optical fiber
No full textA supplementary file is also included.We combine suspended-core microstructured optical fibers with the photoinduced electron transfer (PET) effect to demonstrate a new type of fluorescent optical fiber-dip sensing platform for small volume ion detection. A sensor design based on a simple model PET-fluoroionophore system and small core microstructured optical fiber capable of detecting sodium ions is demonstrated. The performance of the dip sensor operating in a high sodium concentration regime (925 ppm Na+) and for lower sodium concentration environments (18.4 ppm Na+) is explored and future approaches to improving the sensor’s signal stability, sensitivity and selectivity are discussed.Florian V. Englich, Tze Cheung Foo, Andrew C. Richardson, Heike Ebendorff-Heidepriem, Christopher J. Sumby and Tanya M. Monr
Low temperature proton polarized target for nucleon structure studies at COMPASS
No full textTitle: Low temperature proton polarized target for nucleon structure studies at COMPASS Author: Michael Pešek Department / Institute: Department of Low temperature Physics Supervisor of the bachelor thesis: prof. Ing. Miroslav Finger, DrSc., Department of Low Temperature Physics Abstract: Overview of basics of deep inelastic scattering and process of dynamic nuclear polarization with emphasis to importance of precise polarization determination for nucleon spin structure studies are given. This is followed by description of COMPASS experiment with emphasis given to low temperature polarized target. General procedure of NMR data analysis is given and finally polarization for run 2010 and relaxations rates are determined. Keywords: nucleon structure, polarized proton target, low temperatures, NMR techniqu
Multiwavelength gas sensing by rapidly-swept, continuous-wave cavity ringdown spectroscopy
No full textNízkoteplotní polarizovaný terč protonů pro studium struktury nukleonů v experimentu COMPASS
No full textNázev práce: Nízkoteplotní protonový polarizovaný terč pro studium struktury nukleonů v experimentu COMPASS Autor: Michael Pešek Katedra / Ústav: Katedra fyziky nízkých teplot Vedoucí bakalářské práce: prof. Ing. Miroslav Finger, DrSc., Katedra fyziky nízkých teplot Abstrakt: V této práci jsou prezentovány základní přehledy hlubokého nepružného rozptylu a procesu dynamické jaderné polarizace. Je kladen důraz na důležidost určení polarizace pro studium spinové struktury nukleonu. Následuje popis experimentu COMPASS s důrazem na popis nízkoteplotního polarizovaného terče. Je popsána obecná procedura pro určení polarizace a určena polarizace a relaxační doby pro běh experimentu v roce 2010. Klíčová slova: struktura nukleonu, polarizovaný protonový terč, nízké teploty, metoda NMRTitle: Low temperature proton polarized target for nucleon structure studies at COMPASS Author: Michael Pešek Department / Institute: Department of Low temperature Physics Supervisor of the bachelor thesis: prof. Ing. Miroslav Finger, DrSc., Department of Low Temperature Physics Abstract: Overview of basics of deep inelastic scattering and process of dynamic nuclear polarization with emphasis to importance of precise polarization determination for nucleon spin structure studies are given. This is followed by description of COMPASS experiment with emphasis given to low temperature polarized target. General procedure of NMR data analysis is given and finally polarization for run 2010 and relaxations rates are determined. Keywords: nucleon structure, polarized proton target, low temperatures, NMR techniqueKatedra fyziky nízkých teplotDepartment of Low Temperature PhysicsMatematicko-fyzikální fakultaFaculty of Mathematics and Physic
Study of dynamical behaviour of H2O/D2O mixtures by NMR relaxation
No full textTitle: Study of dynamical behavior of H2O/D2O mixtures by NMR relaxation Author: Petr Dvořák Department: Department of Low Temperature Physics Supervisor: doc. RNDr. Jan Lang, Ph.D., Department of Low Temperature Physics Abstract: The subject of this diploma thesis is the chemical exchange in the mixture of light and heavy water, which was studied by methods of high resolution NMR. The first part of this thesis concerns methodology of sample preparation and methodology of measurement of relaxation times of mixture of light and heavy wa- ter. Experimental complications with elution of ions from tube glass, degassing of samples, radiation damping and sample heating by radio-frequency pulses were solved there. In the second part of this thesis the relaxation parameters of chemical exchange of selected sample at various temperatures were measured. Interpretations of experimental data (ionization, molecular clusters and isotopic equilibrium) was suggested. Keywords: NMR, relaxation, water, dynamics, chemical exchang
