We report the first extensive measurements of hyperfine structure in Ta II. Spectra of Ta II were recorded by high-resolution Fourier transform spectrometry in the region 10 000-53 000 cm-1(1886-10 000 Å) and the majority of observed lines show significant hyperfine structure. Computer fits to several hundred of these line profiles have yielded values of the magnetic dipole hyperfine interaction constant A for 88 energy levels with an uncertainty of between 0.5 and 10 per cent for the majority of A factors. The A factors range from −0.078 to +0.065 cm−1 for the even levels and from −0.064 to +0.083 cm−1 for the odd levels. For the majority of these A factors no previous measurements are known. Approximate values of the electric quadrupole hyperfine interaction constant B were found for 73 levels. These measurements of A and B factors allow, for the first time, the effects of hyperfine structure in Ta II lines to be correctly accounted for both in abundance analysis and in the resolution of blended lines in astrophysical spectr
