| The tricarbon molecule,C3,plays an important role in many chemical processes,such as the chemical evolution in the interstellar medium,combustion flames and theoretical calculations.High resolution laser spectroscopic study of C3 can provide precise spectroscopic data for relevant applications,and important information in understanding the structures,bonding properties,and the nature of intramolecular interactions.In order to perform spectroscopic study of C3 with a sub-Doppler resolution,we have developed and constructed a pulsed single longitudinal mode optical parametric oscillator?SLM-OPO?that gives a Fourier transform limited linewidth output over a broadly tunable wavelength range.Using the laser induced fluorescence?LIF?technique,we have systematically studied the sub-Doppler spectra of the A1?u-X1?g+ electronic transition system of C3,not only its main isotopologue but also two 13C mono-substituted isotopologues of 13CCC and C13CC.Molecular data,including transition frequencies and spectroscopic constants,have been accurately determined from the in total 34 band spectra recorded in our experiment.Electromagnetically induced transparency?EIT?with coherently excited molecular system has been observed for the first time by applying the simulated emission pumping?SEP?process to a coherently excited states of C3,whose fluorescence emission exhibits the 'quantum beats' behavior.The main contents of this thesis are as follows:1.Development the SLM-OPOThe SLM-OPO system employs a single frequency 532 nm laser as the pump laser,a bulk KTP crystal as the nonlinear material,and a grazing-incidence-grating Littman type cavity as the oscillator.By spatially filtering the pump laser beam and employing an active cavity-length-stabilization scheme,we have obtained output performances as:a Fourier transform limited bandwidth of less than 0.004 cm-1?120 MHz?,a frequency down conversion efficiency up to 15%,a wavelength coverage of 700-2200 nm and mode-hopping-free tuning range of larger than 20 cm-1.An application of this SLM-OPO to the electronic spectra of SiC2 in a supersonic planar jet shows that a spectral resolution ?v/v?6.2 × 10-7 is achieved2.High resolution spectroscopy of the C3A1?u-X'?g+ transitionC3 molecules are produced in a supersonic jet planar plasma by discharging a 0.3%C2H2/Ar gas mixture,which provides a low vibration-rotational temperature and a reduced Doppler width.High resolution spectra of in total 20 bands in the C3 A1?u-X1?g+ electronic transition system have been experimentally recorded with a resolution of?0.02 cm 1 by LIF.Individual transition frequencies have been extracted from our experimental spectra with an accuracy of?0.005 cm-1.Spectroscopic constants have been determined from detailed rotational analyses.Based on the vibration-rotational combination differences of the hot band transitions,we have also derived the rotational level energies in the excited bending vibrational levels with vibrational quanta up to 5,which data allows to infer the ro-vibrational spectra of C3 in the far infrared region.3.The A1?-X1?+ transition spectra of 13CCC and C13CCUnder the planar plasma jet condition,the two 13C mono-substituted isotopologues of C3,13CCC and C13CC are produced by the discharging 0.3%C2H2/Ar with the isotope 13C in its natural abundance.Benefitting from the detection sensitivity and high spectral resolution in our LIF experiments,spectra of eight A1?-X1?+ electronic transition bands for 13CCC and six bands for C13CC are recorded with a resolution of-0.02 cm-1.Individual transition frequencies,A1? state spectroscopic constants and vibrational frequencies have been determined from detailed rotational analyses.The isotope substitution effect in the A1? state of C3 the electronic structure has also been discussed.4.EIT with the coherently excited state of molecular C3Electromagnetically induced transparency?EIT?with coherently excited molecular system has been observed for the first time from our spectroscopic study of C3.Quantum beats in the fluorescence emission of the A1?u-X1?g+ 02 0-000 transition R?2?and P?4?lines are observed,showing that the upper J'=3 level states involves two coherent levels with an energy interval 41 MHz.By coupling the coherently excited states with an intermediate state of X1?g+ 0622 J = 4 using narrow bandwidth nanosecond laser pulsed,the line profile of the simulated emission spectrum is modulated,and the EIT of the coherently excited state is observed.This result is attributed to the nanosecond laser pulse induced Rabi oscillation,whose frequency is estimated as?1 GHz from the present experiment.In addition,we have also performed high resolution spectroscopic studies of YO,CuSH and SiC2.In the experiment of YO,we have identified a new[33.2]2?electronic state by combing the LIF excitation spectrum,dispersed spectrum and optical-optical double resonance techniques.Using this[33.2]2? state as an intermediate state,high resolution spectra for the A'2?5/2 dark state have also been recorded for the first time using stimulated emission pumping technique.Spectroscopic constants for both states of YO are determined from rotational analysis.In the experiment of CuSH,we have recorded three B1 A'-X1A' transition bands and determined the spectroscopic constants,vibrational frequencies,as well as the molecular geometry of the B1A' state.For SiC2,we have recorded five A1B2-X1A1 transition bands and determined the accurate transition frequencies and spectroscopic constants. |
PDF Full Text Request