Optimization of the Double Pump鈥揚robe Technique: Decoupling the Triplet Yield and Cross Section

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• 作者：Davorin Peceli ; Scott Webster ; Dmitry A. Fishman ; Claudiu M. Cirloganu ; Honghua Hu ; Olga V. Przhonska ; Vladimir V. Kurdyukov ; Yurii L. Slominsky ; Alexey I. Tolmachev ; Alexey D. Kachkovski ; Raghunath R. Dasari ; Stephen Barlow ; Seth R. Marder ; David J. Hagan ; Eric W. Van Stryland
• 刊名：The Journal of Physical Chemistry A
• 出版年：2012
• 出版时间：May 24, 2012
• 年：2012
• 卷：116
• 期：20
• 页码：4833-4841
• 全文大小：533K
• 年卷期：v.116,no.20(May 24, 2012)
• ISSN：1520-5215

文摘

The double pump鈥損robe technique (DPP), first introduced by Swatton et al. [Appl. Phys. Lett.1997, 71, 10], is a variant of the standard pump鈥損robe method but uses two pumps instead of one to create two sets of initial conditions for solving the rate equations, allowing a unique determination of singlet- and triplet-state absorption parameters and transition rates. We investigate the advantages and limitations of the DPP theoretically and experimentally and determine the influence of several experimental parameters on its accuracy. The accuracy with which the DPP determines the triplet-state parameters improves when the fraction of the population in the triplet state relative to the ground state is increased. To simplify the analysis of the DPP, an analytical model is presented, which is applicable to both the reverse saturable and the saturable absorption regimes. We show that the DPP is optimized by working in the saturable absorption regime. Although increased accuracy is in principle achievable by increasing the pump fluence in the reverse saturable absorption range, this can cause photoinduced decomposition in photochemically unstable molecules. Alternatively, we can tune the excitation wavelength to the spectral region of larger ground-state absorption, to achieve similar accuracy. This results in an accurate separation of triplet yield and excited-state absorption cross section. If the cross section at another wavelength is then desired, a second pump鈥損robe experiment at that wavelength can be utilized given the previously measured triplet yield under the usually valid assumption that the triplet yield is independent of excitation wavelength.