Getting to the (Square) Root of the Problem: How to Make Noncoherent Pumped Upconversion Linear
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- 作者：Alexandre Haefele ; J枚rg Blumhoff ; Rony S. Khnayzer ; Felix N. Castellano
- 刊名：The Journal of Physical Chemistry Letters
- 出版年：2012
- 出版时间：February 2, 2012
- 年：2012
- 卷：3
- 期：3
- 页码：299-303
- 全文大小：298K
- 年卷期：v.3,no.3(February 2, 2012)
- ISSN：1948-7185
文摘
We present experimental data illustrating that photochemical upconversion based on sensitized triplet鈥搕riplet annihilation can exhibit anti-Stokes emissions whose intensities with respect to the excitation power can vary between quadratic and linear using a noncoherent polychromatic light source. The benchmark upconverting composition consisting of Pd(II) octaethylporphyrin (PdOEP) sensitizers and 9,10-diphenylanthracene (DPA) acceptors/annihilators in toluene was selected to generate quadratic, intermediate, and linear behavior under both coherent and noncoherent excitation conditions. Each of these power laws was traversed in a single sample in one contiguous experiment through selective pumping of the sensitizer using an Ar<sup>+sup> laser. Wavelength-dependent responses ranging from quadratic to pseudolinear were also recorded from the identical sample composition when excited by Xe lamp/monochromator output in a conventional fluorimeter, where the optical density at 位<sub>exsub> dictates the observed incident power dependence. Finally, pure linear behavior was derived from noncoherent excitation for the first time at higher sensitizer concentrations.