Focusing, rotational state selection and orientation of CH3I in a seeded supersonic beam
1982; Elsevier BV; Volume: 68; Issue: 1-2 Linguagem: Inglês
10.1016/0301-0104(82)85075-1
ISSN1873-4421
AutoresK. K. Chakravorty, David H. Parker, Richard B. Bernstein,
Tópico(s)Advanced Chemical Physics Studies
ResumoRotationally cool methyl iodide molecules from a seeded, supersonic nozzle beam source are focused and state-selected using the hexapole electric field tecnique of Kramer and Bernstein. The narrow speed distributions obviate the use of a mechanical velocity selector. A quantitative computer simulation of the focusing curves (transmitted intensity versus hexapole rod voltage V0), based on the trajectory method of Brooks , yields the rotational state distributions of the transmitted beams. These results establish confidence in the calculated values of the average molecular alignment of the molecules passing into orientation field, within which (using a crossed beam arrangement) oriented-molecule collisions may be carried out. For a CH3I beam (rotational temperature 23 K), state-selected and focused at V0 = 2 kV, the average value of the molecular alignment is found to be (cos θ> = 0.64: ± 0.01. The most abundant J, K, M quantum states in the focused beam are (2,2,2) (3,3,3) and (1,1,1), respectively. These three states alone account for over 90% of the transmitted CH3I molecules.
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