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Cathodoluminescence of synthetic zircon implanted by He+ ion

Tsuchiya Y., Kayama M., Nishido H., Noumi Y.

Geochronometria

2017

Vol. 44, no. 1

129--135

He+ ion implantation at 4.0 MeV, equivalent to energy of α particles from natural radioactive nuclei 238U and 232Th, has been conducted for undoped synthetic zircon. The cathodoluminescence (CL) of implanted samples was measured to clarify the radiation-induced effects. Unimplanted synthetic zircon shows pronounced and multiple blue emission bands between 310 nm and 380 nm, whereas the implanted samples have an intense yellow band at ~550 nm. The blue emission bands can be assigned to intrinsic defect centers formed during crystal growth. The yellow band should be derived from induced-defect centers by He+ ion implantation, which might be related to the metamicitization originated from a self-induced radiation in natural zircon. The yellow band may be separated into two emission components at 1.96 eV and 2.16 eV. The emission component at 2.16 eV is recognized in both unimplanted and implanted samples, and its intensity increases with an increase in the implantation dose. The CL of zircon can be used as the geodosimeter.

Response of cathodoluminescence of alkali feldspar to He+ ion implantation and electron irradiation

Kayama M., Nishido H., Toyoda S., Komuro K., Finch A. A., Lee M. R., Ninagawa K.

Geochronometria

2013

Vol. 40, no. 4

244--249

Cathodoluminescence (CL) of minerals such as quartz and zircon has been extensively studied to be used as an indicator for geodosimetry and geochronometry. There are, however, very few investigations on CL of other rock-forming minerals such as feldspars, regardless of their great scientific interest. This study has sought to clarify the effect of He+ ion implantation and electron irra-diation on luminescent emissions by acquiring CL spectra from various types of feldspars including anorthoclase, amazonite and adularia. CL intensities of UV and blue emissions, assigned to Pb2+ and Ti4+ impurity centers respectively, decrease with an increase in radiation dose of He+ ion implantation and electron irradiation time. This may be due to decrease in the luminescence efficiencies by a change of the activation energy or a conversion of the emission center to a non-luminescent center due to an alteration of the energy state. Also, CL spectroscopy of the alkali feldspar revealed an in-crease in the blue and yellow emission intensity assigned to Al-O−-Al/Ti defect and radiation-induced defect centers with the radiation dose and the electron irradiation time. Taken together these results indicate that CL signal should be used for estimation of the α and β radiation doses from natural radi-onuclides that alkali feldspars have experienced.