Search for the $^{3}He$ isotope in the atmospheres of HgMn stars

We carried out a detailed analysis of the helium lines at 4921, 5876 and 6678 A in the spectra of the HgMn stars HD 58661, HD 172044, HD 185330 and HD 186122. For the first of these lines, the isotopic shift reaches +0.33 A for pure 3He, while for the last one, the maximum shift is +0.50 A. The 5876 line does not show any significant isotopic shift and is chosen for comparison. No trace of 3He was found in the atmosphere of HD 172044, while its presence was confirmed in HD 185330. This isotope is clearly present in the atmosphere of HD 58661. The results obtained for HD 186122 were ambiguous, 3He being apparently present in the 4921 line but not in the 6678 line, possibly because the latter is very weak