Vibrational Spectra Of Ethylbenzene And P-difluorobenzene And The Application

Environmental endocrine disruptors (EEDs) are a kind of exogenous hormone which can interfere with the synthesis, secretion, transport, action and elimination of natural hormone in creatures including humans. It affects the function of the reproduction, nervous and immune system and is closely related to the life of human. It’s meaningful to study on EEDs. Ethylbenzene and p-difluorobenzene belong to the family of EEDs. Researches on structures, vibrational frequencies, excited states energies and molecular orbitals contribute to the comprehension of the molecular physical and chemical properties. These researches can give out an important application in pollutant concentration detection. This dissertation is mainly composed of three parts:The first part is the research on the structure and vibrational spectra of ethylbenzene. The vibrational spectra over a range of2000cm"1of ethylbenzene in the first excited state are obtained by the one-color two-photon resonance ionization. The obtained band origin is37586±3cm-1. Ab initio calculations are taken out simultaneously on the optimized structures, vibrational spectra, transition energies of the excited state and molecular orbitals using density function theory. The peaks obtained from the experiment have been successfully assigned with the help of theoretical calculation results.The second part is the research on the vibrational spectra and structure of p-difluorobenzene. The geometrical configurations of the ground and excited states have been optimized by Hartree-Fock and configuration interaction singles methods. Then the vibrational frequencies have been predicted based on these optimized structures. The orbitals and transition energies of the excited states are calculated by configuration interaction singles and density function theory methods. The vibrational spectra over a range of2200cm"1in the first excited state of p-difluorobenzene are obtained by the one-color two-photon resonance ionization. The peaks obtained have been assigned successfully with the help of theoretical calculation results.The third part is the determination on the lowest limit of the experimental apparatus about the concentration detection. We set the laser wavelength in the mode510of p-difluorobenzene and prepare the mixed sample gas in several concentrations. The signal of the parent ion in each concentration has been measured and obtained. Through the numerical analysis, the obtained minimum detective content of p-difluorobenzene is3.125ppb which corresponds to28ng/L.