  Atomic defect centers in diamond have been widely exploited in numerous
quantum applications like quantum information, sensing, quantum photonics and
so on. In this context, there is always a requirement to improve and optimize
the preparation procedure to generate the defect centers in controlled fashion,
and to explore new defect centers which can have the potential to overcome the
current technological challenges. Through this letter we report enhancing the
concentration of Ge and Xe vacancy centers in nanocrystalline diamond (NCD) by
means of He+ irradiation. We have demonstrated controlled growth of NCD by
chemical vapor deposition (CVD) and implantation of Ge and Xe ions into the
CVD-grown samples. NCDs were irradiated with He+ ions and characterized through
optical spectroscopy measurements. Recorded photoluminescence results revealed
a clear signature of enhancement of the Xe-related and Ge vacancies in NCDs.
