High resolution spectroscopy for novel excitation modes of nuclei: results and challenges

The appearance of collective excitation with a discrete spectrum is a characteristic feature of a mesoscopic system. The long wavelength part of these collective modes, being strongly dependent on the system shape, have attracted attention in a wide variety of mesoscopic systems at different length scales, such as, quantum dots (nanometer scale) to atomic nuclei (femtometer scale). The atomic nucleus is one of the well studied mesoscopic systems, which continues exhibiting new collective modes due to improved experimental techniques. In this presentation, we will describe some of the recent results on novel modes of nuclei from experiments which have been carried out with the digital INGA (Indian National Gamma Array). The relation between the observed spectra and the different symmetries related to the shapes of these nuclei will be discussed. Looking into the future, we will talk about the challenges in understanding the richness of spectra of exotic nuclei and our plans for participation in the next generation of gamma spectrometers required for such studies.