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Experimental f-value and isotopic structure for the Ni I line blended with [OI] at 6300A

We have measured the oscillator strength of the Ni I line at 6300.34 Å, which is known to be blended with the forbidden [O I] $λ$6300 line, used for determination of the oxygen abundance in cool stars. We give also wavelengths of the two isotopic line components of $^{58}$Ni and $^{60}$Ni derived from the asymmetric laboratory line profile. These two line components of Ni I have to be considered when calculating a line profile of the 6300 Å feature observed in stellar and solar spectra. We also discuss the labelling of the energy levels involved in the Ni I line, as level mixing makes the theoretical predictions uncertain.