The developl)lent of powerfiJi heavy-ion accelerators and multi-detector systems had arnstrong impact on y-ray spectroscopy. Via heavy-ion fusion-evaporation reactions one canrnproduce very high-spin nuclear states. The highly excited nuclei then emit generally a largernnumber of y-rays, and the spectJ1JJn measured is a combination of different nuclear reactionrnchannels. Consequently,y-ray singles spectra are too complicated to identifY transitions atrnhigh spin which are usually weak. Therefore, multi-detector with high resolution, goodrndetector response and good efficiency are required to investigate such spectra. Some of thernmulti-detector arrays are therefore discussed in this work.rnWith the help of multi-detector systems high-spin states of nuclei have been studied inrndifferent mass regions. The mass A " 80 region is one of them where a number ofrninteresting features have been observed, and this work is also devoted to this region. Hence,rnexperimental and theoretical reviews of this mass region is included.rnIn the data analysis part a singles spectJ1JJTI obtained from an in-beam measurement at 90Â°rnvia the 'Li + "Se fusion-evaporation reaction at 35 MeV is analyzed with the softwarernpackage GANAAS. The energies and intensities ofy-lines of selected nuclei obtained fromrnGANAAS fits are compared with published data, and most of the lines that are accessiblernfi'ol11 the singles spectrum are found to be in a good agreement with other results