Natural fluorite, anhydrite and apatite under deep UV excitation exhibits several narrow emission bands in the spectral range of 225–300 nm with the strongest peaks at 230–240 nm and 260–290 nm and with half-widths of 20–30 nm. They are characterized by narrow excitation band peaking at 220 nm and very short decay times of 20–50 ns. Those spectral-kinetic parameters enable their interpretation as 4f5d–4f transitions in Pr3+ luminescence center. Such kind of luminescence has been studied extensively over the past several decades in synthetic phosphors, including those which are analogous to natural compounds, but it is the first time 5d–4f luminescence transitions of Pr3+ is being proved in minerals.

中文翻译：

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Pr3+ 在天然萤石 CaF2、硬石膏 CaSO4 和磷灰石 Ca5(PO4)3F 中 5d-4f 跃迁的发光

在深紫外激发下，天然萤石、硬石膏和磷灰石在 225-300 nm 的光谱范围内表现出几个窄的发射带，最强的峰位于 230-240 nm 和 260-290 nm，半宽为 20-30 nm。它们的特征是在 220 nm 处达到峰值的窄激发带和 20-50 ns 的非常短的衰减时间。这些光谱动力学参数可以将它们解释为 Pr3+ 发光中心的 4f5d–4f 跃迁。在过去的几十年里，这种发光在合成磷光体中得到了广泛的研究，包括那些类似于天然化合物的磷光体，但这是第一次在矿物中证明 Pr3+ 的 5d-4f 发光跃迁。