Fig. 3: Linewidths of the spectral profiles of two \(\bar{p}{{}^{4}{\rm{H}}{\rm{e}}}^{+}\) laser transitions as a function of the He I or He II target temperature. | Nature

Fig. 3: Linewidths of the spectral profiles of two \(\bar{p}{{}^{4}{\rm{H}}{\rm{e}}}^{+}\) laser transitions as a function of the He I or He II target temperature.

From: High-resolution laser resonances of antiprotonic helium in superfluid 4He

Fig. 3

a, b, The FWHM Lorentzian linewidths of the transition (n, ℓ) = (37, 35) → (38, 34) (a) and (n, ℓ) = (39, 35) → (38, 34) (b). In normal liquid helium the temperature dependence of the linewidth was well approximated by a single exponential (indicated by the blue curve), whereas in superfluid helium a characteristic dependence with the smallest linewidths at temperatures between T = 1.7 K and 1.9 K was observed. Error bars, 1 s.d.

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