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Ultraviolet absorption and luminescence of matrix-isolated adenine

机译：基质分离的腺嘌呤的紫外吸收和发光

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We have investigated the absorption, the fluorescence and phosphorescence emission and the fluorescence lifetimes of adenine in low-temperature argon and nitrogen matrices at 15 K. Compared to other environments the absorption spectrum shows higher intensity at the shortest wavelengths, and a weak apparent absorption peak is observed at 280 nm. The resolved fluorescence excitation spectrum has five peaks at positions corresponding to those observed in the absorption spectrum. The position of the fluorescence maximum depends on the excitation wavelength. Excitation below 220 nm displays a fluorescence maximum at 305 nm, while for excitations at higher wavelengths the maximum occurs at 335 nm. The results suggest that multiple-emission excited electronic states are populated in low-temperature gas matrices. Excitation at 265 nm produces a phosphorescence spectrum with a well-resolved vibrational structure and a maximum at 415 nm. The fluorescence decays corresponding to excitation at increasing energy of each resolved band could be fit with a double exponential, with the shorter and longer lifetimes ranging from 1.7 to 3.3 ns and from 12 to 23 ns, respectively. Only for the excitation at 180 nm one exponential is required, with the calculated lifetimes of 3.3 ns. The presented results provide an experimental evidence of the existence of multiple site-selected excited electronic states, and may help elucidate the possible deexcitation pathways of adenine. The additional application of synchrotron radiation proved to result in a significant enhancement of the resolution and spectral range of the phenomena under investigation.
机译：我们已经研究了低温氩气和氮气基质中15 K时腺嘌呤的吸收，荧光和磷光发射以及荧光寿命。与其他环境相比，吸收光谱在最短波长下显示出更高的强度，并且表观吸收峰较弱。在280nm处观察到。解析的荧光激发光谱在与吸收光谱中观察到的那些位置对应的位置具有五个峰。荧光最大值的位置取决于激发波长。低于220 nm的激发在305 nm处显示荧光最大值，而对于较高波长的激发，在335 nm处出现最大值。结果表明，在低温气体基质中存在多发射激发电子态。在265 nm处激发产生具有良好解析的振动结构且在415 nm处具有最大值的磷光光谱。对应于在每个分辨带的能量增加时激发的荧光衰减可以用双指数拟合，其较短和较长的寿命分别为1.7至3.3 ns和12至23 ns。仅对于180 nm处的激发，需要一个指数，计算出的寿命为3.3 ns。提出的结果提供了多个位点选择的激发电子态的存在的实验证据，并可能有助于阐明腺嘌呤的可能的去激励途径。事实证明，同步加速器辐射的附加应用可显着提高所研究现象的分辨率和光谱范围。

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