طيف سنجي ليزري نئون و بنزآلدئيد پرتون دار و بيناب نمايي هليم با تابش سينكروترون

چكيده انگليسي :

Laser Spectroscopy of Neon and Protonated Benzaldehyde and Spectroscopy of Helium Using Synchrotron Radiation Reza Omidyan E mail omidyan@ch iut ac ir Date of Submission November 20 2009 Department of Chemistry Isfahan University of Technology 84156 83111 Isfahan Iran1st Supervisor Prof Mahmoud Tabrizchi E mail m tabriz@cc iut ac ir2nd Supervisor Dr Hossein Farrokhpour E mail h farrokh@cc iut ac irDepartment Graduate Coordinator Prof Bijan NajafiDepartment of Chemistry Isfahan University of Technology Isfahan 84156 83111 Iran fax 983113912350Abstract In the first part of this work eleven two photon transitions originating from the 2p53s 3 2 2 2p53s 1 2 0 2p53s 3 2 1 and 2p53s 1 2 1 states to the 2p54d configuration states of neon have been investigated usingoptogalvanic spectroscopy in the visible region 570 626 nm The two photon assignments were confirmed byevaluating the temporal evolution power dependency and line widths of the optogalvanic signals In order tostudy the dynamics of plasma temporal evolution of two photon optogalvanic signals of neon was alsoevaluated Optogalvanic signals for four transitions from the metastable 2p53s 3 2 2 state to 2p54d0 3 2 1 2p54d0 3 2 2 2p54d0 5 2 3 and 2p54d0 5 2 2 states were recorded over a range of discharge currents 3 4 9 mA It was found that the shape of the optogalvanic signal was strongly dependent on the discharge current In the second part synchrotron radiation was used to obtain the spectra of triplet and singlet metastablehelium atoms resonantly photoexcited to doubly excited states The first members of three dipole allowed 1 3Pseries have been observed and their relative photoionization cross sections determined both in the triplet from1s2s 3S and singlet from 1s2s 1S manifolds The intensity ratios were drastically different with respect totransitions from the ground state When radiation damping is included the results for the singlet are in agreementwith theory while for triplets spin orbit interaction must also be taken into account In the final part of this thesis The photo dissociation spectroscopy of the protonated benzaldehye wasinvestigated The spectrum of protonated benzaldehyde was recorded in the 435 385 nm wavelength range Thefirst excited state is a state strongly red shifted compared to the state of neutral benzaldehyde Thespectrum presents well resolved vibronic bands in contrast to some other protonated aromatic molecules likebenzene or tryptophan in which the excited state dynamics is so fast that no vibrational structure can beobserved The bands can be assigned on the basis of a Franck Condon analysis using ground and excited statefrequencies calculated at the CC2 TZVP level Keywords optogalvanic spectroscopy doubly excited states photo dissociation heliumIntroduction The OG effect is the change in the current pass through a gas filled electrical due to changes in theeffective ionization rates induced by laser light tuned resonantly to specific atomic or molecular transition of thedischarge medium Such a laser illumination usually causes an increase in the population of the highly excitedlevels which enhances the ionization and causes a voltage drop Over the years many investigations have beencarried out to observe the OG lines of noble gases such as neon and argon extending from the ultra violet to thered spectral region B Barbieri et al Rev Mod Phys 1990 Another significant aspect related to the optogalvanic effect is the study of discharge mechanism whichhelps a better understanding of atomic and collisional processes in plasma In this regard many theoretical andanalytical models based on experimental observations have been developed These models characterize theresponse of discharge when steady state population distribution of the energy levels is perturbed by a radiationresonant to a transition between these levels Ben Amar et al proposed a four state phenomenological model tounderstand and describe the details of the optogalvanic signal A Ben Amar et

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طيف سنجي ليزري نئون و بنزآلدئيد پرتون دار و بيناب نمايي هليم با تابش سينكروترون

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