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MO: Fachverband Molekülphysik
MO 21: Astrophysics and Ions
MO 21.5: Vortrag
Freitag, 13. März 2020, 15:15–15:30, f142
Towards para-ortho conversion in ammonia — •Guang Yang1,4, Dominic Laumer2,4, Christoph Heyl2, Andrey Yachmenev1,3, Ingmar Hartl2, and Jochen Küpper1,3,4 — 1Center for Free-Electron Laser Science, DESY, Hamburg — 2DESY, Hamburg — 3The Hamburg Center for Ultrafast Imaging, Hamburg — 4Department of Physics, Universität of Hamburg, Hamburg
The spectrum of ammonia can be considered as the combination of the spectra of two distint molecules, para and ortho, which have different total-nuclear-spin number I=1/2 and I=3/2, respectively, of the three hydrogen atoms. It is considered a good approximation that interconversions of nuclear spin isomers are forbidden. However, weak hyperfine couplings weakly allow the conversion happen.
We present a combined theoretical and experimental study of the hyperfine-resolved spectrum of ammonia. The calculations have been performed using the variational approach TROVE, a new spectroscopically determined potential energy surface, and ab initio quadrupole, spin-spin, and spin-rotation coupling surfaces. For the spectroscopic observation of the para-ortho conversion, we utilized a mid-infrared frequnecy-comb Fourier-transform spectrometer [2] to perfom first survey scans of the absorption spectrum in the 4 µm region. We investigated the self-broadening and self-shift. Currently, we are optimizing the experimental setup to improve the resolution and sensitivity and search the weak para-ortho conversion lines.
[1] S. N. Yurchenko, et al., J. Mol. Spectrosc., 245, 126 (2007)
[2] V. Silva de Oliveira, et al., arXiv:1904.02611, (2019)