Infrared Mn I laboratory oscillator strengths for the study of late type stars and ultracool dwarfs

Aims: The aim of our new laboratory measurements is to measure accurate absolute oscillator strengths for neutral manganese transitions in the infrared needed for the study of late-type stars and ultracool dwarfs. Methods: Branching fractions have been measured by high resolution Fourier transform spectroscopy and combined with radiative level lifetimes in the literature to yield oscillator strengths. Results: We present experimental oscillator strengths for 20 transitions in the wavelength range 3216 to 13 997 Å, 15 of which are in the infrared. The transitions at 12 899 Å  and 12 975 Å  are observed as strong features in the spectra of late-type stars and ultracool dwarfs. We have fitted our calculated spectra to the observed lines in spectra of late-type stars. Using the new experimentally measured log(gf) values together with existing data for hyperfine structure splitting factors we determined the manganese abundance to be log N(Mn) = -6.65 ± 0.05 in the atmosphere of the Sun, log N(Mn) = 6.95 ± 0.20 in the atmosphere of Arcturus, and log N(Mn) = -6.70 ± 0.20 in the atmosphere of M 9.5 dwarf 2MASSW 0140026+270150.