Two-Photon Chemistry of Small Organic Chromophores

通常情况下，分子可以通过吸收能量与这两种状态之间的能量差相匹配的光(或光子)来诱导分子从正常的基态进入激发态。然而，正如诺贝尔奖获得者玛丽亚·戈珀特·梅耶尔在1930年的《S》中预测的那样，有时(取决于分子的性质)可以用两个光子诱导从基态到激发态的变化，每个光子的能量大约是所需能量的一半，这一过程被称为双光子吸收。由于双光子吸收(2PA)比传统的单光子吸收(1PA)具有更多的优点：由于更高的穿透能力，2PA所需的较低能量与生物系统中的光化学更兼容，并且对双光子的要求提供了更强的照射微观区域的能力，从而提高了照射的准确性。这些优势导致了双光子化学在不同领域的广泛应用，从健康相关领域(光动力学治疗)到高科技领域(3D数据存储)。

Normally, a molecule can be induced to go from its normal ground state to an excited state by absorbing light (or a photon) with energy that matches the difference in energy between those two states. However, as predicted by Nobel laureate Maria Goeppert Mayer in the 1930's, the change from ground state to excited state can sometimes (depending on the properties of the molecule) be induced using two photons with each photon having about half the needed energy in a process called two-photon absorption. There is intense interest in this phenomena, since two-photon absorption (2PA) has several advantages over the more conventional one-photon absorption (1PA): the lower energy needed for 2PA is more compatible with photochemistry in biological systems due to the higher penetration abilities, and requirement for two-photons provides a much greater ability to irradiate microscopic areas, thus increasing the accuracy of irradiation. These advantages have led to a wide range of applications of two-photon chemistry in diverse areas ranging from health related fields (photodynamic therapy) to high tech fields (3D data storage).