# TIME RESOLVED MMW/MMW DOUBLE RESONANCE SPECTROSCOPY ON METHYL FLOURIDE: OBSERVATION OF A K-CHANGING COLLISION PROCESS

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 Title: TIME RESOLVED MMW/MMW DOUBLE RESONANCE SPECTROSCOPY ON METHYL FLOURIDE: OBSERVATION OF A K-CHANGING COLLISION PROCESS Creators: Mengel, M.; Ball, C. D.; De Lucia, Frank C. Issue Date: 1999 Publisher: Ohio State University Abstract: We report our recent experiments to measure directly collisional relaxation rates of methyl flouride $(CH_{3}F)$ in collision with Helium at low temperatures $(2-20 K)$ using time resolved millimeter/millimeter wave double resonance spectroscopy and employing the collisional cooling technique. This system uses a BWO synthesizer and a ferrite waveguide switch to generate the pulsed pump radiation. The collisional relaxation can be monitored using a klystron based millimeter wave harmonic generator. We will discuss our current results for relaxation rates where we pump the $J =2 \rightarrow 3$ transitions and probe the $J = 3 \rightarrow 4$ aswell as the $J = 4 \rightarrow 5$ transitions of the methyl flouride molecule within the K -states 0,1 and 2. We will emphazise the observation of probe signals in a transition with $K = 2$ upon pumping a transition in $K = 1$. Since there are no dipole allowed radiative transfer processes between states with different K, we must assume K -changing collisions of methyl flouride with Helium to explain this. We will also report theoretical studies which employ the solution of the Master equation for the population flow of a multilevel system in order to justify the analytical procedure we use to generate rate constants from the observed time dependent probe signals. Description: $^{a}$ current address: Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA Author Institution: Department of Physics, The Ohio State University URI: http://hdl.handle.net/1811/19444 Other Identifiers: 1999-TC-02