Theoretical Researches On New Trap Scheme Of Cold Molecules And Experimental Preparation,Spectra Research Of Ch Radical

Cold molecules have many important applications in the field of science, such as high-resolution spectrum, cold chemistry, cold collision, quantum computation, quantum information processing and the measurement of fundamental physical constants. In this thesis, methods of preparing cold molecules and trapping of neutral molecules are first reviewed, the applications of cold molecules are also introduced. Then two new schemes of trapping cold polar molecules are proposed. After that, an important molecule(CH radical) which can be used for Stark deceleration and manipulation is introduced. Two methods for CH radical production are used:the DC pulse discharge and the photodissociation using the fifth harmonic YAG laser. Summary and outlook are given in the end.Using two charged stainless steel rings and a grounded metal plate, an optically accessible and controllable electrostatic surface storage ring for cold polar molecules can be formed on a chip. The spatial distribution of the electrostatic fields is numerically calculated. Relationships between the height of the trap center above the chip surface and the setup parameters are investgated in detail. The motion of the molecules in the storage ring is numerically simulated with OH radical molecules as a tester. Dependencies of molecular translational temperature and their trapping efficiency on parameters of the trap setup and the initial distribution of cold molecules are analyzed. Numerical simulations indicate that the number of round trips a trapped molecular packet makes can be improved significantly by incorporating bunching function into the scheme. Another scheme of a controllable high-efficient electrostatic surface trap for cold polar molecules on a chip is also studied, which consists of three charged rings and two insulating substrates. The electric fields and corresponding trapping potential for ND3molecules of J, K M>=|1,-1> state are calculated. The dependence of the effective well depth on the system parameters is analyzed. Monte-Carlo simulation shows that the loading efficiency of molecules into the trap can as high as-90%with a translational temperature of cold molecules being-14mK. Adiabatic cooling is numerically simulated by decreasing the trap depth and the temperature of the trapped molecules drops from34.5mK to5.8mK.Experimental study of production of CH radicals is performed using the method of DC pulse discharge. Experimental data are compared to the simulated ones given by the LIFBASE software and the vibrational and rotational temperatures of CH(A2△) product are obtained. The relationships between the CH(A2Λ) emission spectrum intensity and the experimental parameters are studied, such as the discharge duration, the time delay between the trigger of the pulse valve and the discharge and the voltage of discharge.Using the tool of resonance enhanced multiphoton ionization(REMPI), we study the REMPI of CH radical.Finally, The fifth harmonic YAG laser is used to produce CH (A2△) by multiphoton dissociation of (CH3)2CO, CH3NO2, CH2Br2and CHBr3respectively. The emission spectrum of CH (A2△) is acquired and analyzed. The dependence of fluorescence intensity on pulse energy of the laser is studied and the probable dissociation channels are analyzed. The relationships between the fluorescence intensity and some parameters are studied, such as the temperature of the beam source, stagnation pressure and the delay between the trigger of pulse valve and the laser. The role that the carrier gases play during the photodissociation is analyzed. The vibrational and rotational temperatures of CH(A2△) are obtained by comparing experimental data to simulated ones from the LIFBASE program.