This thesis reports on the term analysis of singly-ionised manganese carried out in order to improve the accuracy and completeness of available Mn II atomic wavelengths and energy levels, for astrophysical applications. An extensive analysis of the Mn spectrum was carried out using high-resolution Fourier Transform (FT) spectra, supplemented with grating measurements, of Mn(Ne) and Mn(Ar) hollow cathode discharge sources, over the range 1820 – 121728 cm-1.

The analysis of these spectra has resulted in accurate wavelength measurements for a total of 2360 Mn II lines of which 1219 are measured through FTS. These wavelengths are given to at least an order of magnitude greater accuracy compared with previous measurements. Energy level values have been revised for a total of 477 levels with typical uncertainties found to ~few mK (0.001 cm-1). In addition, 27 new energy level values of Mn II have been found from which 213 Mn II lines have been newly classified. This analysis has also enabled 56 Mn II energy levels, previously established through observation of stellar spectra alone, to be verified using laboratory-measured high-resolution FTS wavelengths.