Rotational State Selection Of Molecules By Electrostatic Hexapole And Proposal Of Orientation And Alignment Of State-selected Molecules

We can obtain molecules with certain rotational states, even with apure rotational state by using electrostatic hexapole to focus polarmolecules. And then use them to study molecule reaction dynamics andanalyze the structure of molecules and so on.In this thesis, we studied the focusing curves of two linear molecules(NO and OCS) and a symmetry top molecule ě by electrostatichexapole. Comparing the theoretical simulation with the experimentaldata, we found that different rotational states could be focused at differentvoltage via Stark effect. For NO, we obtained a pure rotational state in therising part and the first wave of the focusing curve, respectively. For OCSand ě, there were several rotational states contributing to the risingpart of their focusing curves. In order to get more pure population on asingle rotational state, we could lower the rotational temperature of themolecular beam or increase the beam velocity.The second part of this thesis gives the next step experimentalpropose of our laboratory. First we will get NO molecules with a singlerotational state by the hexapole machine. And then orient the NOmolecules by dc electric fields at13KV/cm. We can get the data of the degree of orientation by pump-probe method and Velocity Map Imaging(VMI).