Hello,
I am working at the EPFL in Lausanne Switzerland. I am using cavity
ring-down spectroscopy to take spectra of methane in a free jet
expansion.
We are interested in determining the rotational temperature of our jet
expansion. We are using CRDS of the Q-branch of the first overtone of
the nu3 vibration of methane to determine relative populations of
rotational states.
What I need is a relatively simple computer program or equation which
will accurately simulate the rotational methane spectrum at a given
temperature.
The information which we get out of our experiment is the intensities of
Q(1) through Q(8) of the 2nu3 transition and we would like to fit these
experimental intensities to a calculated temperature.
What complicates the standard Boltzmann distribution are the following:
-methane exists in three spin states which do not interconvert (which
means that at 0 K, there is still significant intensity in Q(1) and Q(2)
-the Hoenl-London factors for spherical top molecules are not
necessarily evident.
Any insight into the simulation, the appropriate equation, or an already
written computer simulation would be most appreciated.
Thank you for your time.
Sincerely,
Jordan Katz
Laboratoire de Chimie Physique Moleculaire
Ecole Polytechnique Federale de Lausanne
CH-1015 Lausanne Switzerland
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tel 41 (0)21 693 3116
fax 41 (0)21 693 5170
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