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arXiv · 1604.04900

Collisional shift and broadening of the transition lines in pionic helium

Boyan Obreshkov·Dimitar Bakalov
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Abstract

We calculate the density shift and broadening of selected dipole transition lines of pionic helium in gaseous helium at low temperatures up to T=12 K and pressure up to a few bar. In the approximation of binary collisions the shift and broadening depend linearly on the density; we evaluate the slope of this linear dependence for a few spectral lines of known experimental interest, and also investigate its temperature dependence. We find a blue shift of the resonance frequencies of the $(n,l)=(16,15) \rightarrow (16,14)$, $(17,16) \rightarrow (17,15)$, and $(16,15)\rightarrow(17,14)$ unfavored transitions, and a red shift for the favored one $(17,16) \rightarrow (16,15)$. The results are intended to significantly increase the efficiency of the laser spectroscopy investigations of pionic helium and help the interpretation of the experimental data.

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Boyan Obreshkov, Dimitar Bakalov. 2016-04-17. Collisional shift and broadening of the transition lines in pionic helium. https://doi.org/10.1103/physreva.93.062505

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