Up-conversion and excited state energy transfer in rare-earth doped materials
Up-conversion and excited state energy transfer in rare-earth doped materials
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DOI：
10.1007/bfb0111143
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发表时间：
1976
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影响因子：
--
通讯作者：
J. C. Wright
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文献类型：
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作者：
J. C. Wright
稀土离子在光谱上是独特的，因为4f“核心内的光学活性跃迁被很好地屏蔽了，不受外部影响。当离子被掺杂到晶格中时，这种隔离导致观察到尖锐的线条[4.1，]。然而，有一些重要的过程，如敏化和荧光猝灭，依赖于稀土离子之间的非常小的相互作用。荧光敏化和猝灭都涉及两个离子，一个处于激发态，另一个处于基态。最近，人们发现了涉及两个激发离子之间相互作用的新过程。虽然这种过程在早期工作中并不重要，但近年来随着能够产生高激发密度的高强度窄带激光光源的出现，它们变得非常重要。这些工艺已被用于敏化激光操作[4.2，]，开发新的红外到可见光荧光粉[4.3-]，提高红外量子计数器(IRQC)[4.4-]的灵敏度(尽管它们也会限制性能)[4.5-]，并创造新的猝灭机制[4.6，7，]。稀土离子中普遍存在的能级的复杂性使得激发态相互作用在高激发材料中是一个非常普遍的过程。在本文中，我们将尝试了解对这些过程非常重要的基本机制。在第一节中，我们将观察到已观察到的各种能量转移现象，并透视激发态相互作用。在下一节中，我们将研究离子之间发生的基本相互作用。在第三部分中，我们将讨论能量传递中重要的一般过程，并讨论相互作用的数学描述。最后，我们将具体研究激发态相互作用，并列举一些重要的激发态相互作用的例子，以了解可用于分析它们的机制和实验步骤。
The rare-earth ions are unique spectroscopically because the optically active transitions within the 4f" core are well-shielded from outside influences. This isolation results in the sharp lines that are observed when the ions are doped into crystalline lattices [4.1,]. There are, however, important processes such as sensitization and quenching of fluorescence that rely upon the very small interactions between rare-earth ions. Both fluorescence sensitization and quenching involve two ions, one in an excited state and one in the ground state. Recently, new processes have been found that involve interaction between two excited ions. Although such processes were not of importance in early work, they have become very important in recent years with the advent of intense, narrow-band laser sources which are capable of creating high excitation densities. These processes have been used to sensitize laser operation [4.2,], develop a new series of infrared to visible phosphors [4.3-], increase sensitivity of infrared quantum counters (IRQC)[4.4-](although they can also limit performance as well)[4.5-], and create new quenching mechanisms [4.6, 7,]. The complexity of levels that are generally present in rare-earth ions makes excited state interactions a very general process in highly excited materials. In this article, we will try to understand the basic mechanisms that are important for these processes. In the first section, we will look at the wide variety of energy transfer phenomena that have been observed and place the excited state interactions in perspective. In the next section, we will examine the basic interactions that occur between ions. In the third section, the general processes of importance in energy transfer will be discussed and the mathematical description for the interactions will be treated. Finally, excited state interactions will be studied specifically and some examples of the important excited state interactions will be presented to understand the mechanisms and experimental procedures available for analyzing them.