Observation of the Lowest Lying Electric-Dipole-Allowed Two-Photon Resonance in C60
Observation of the Lowest Lying Electric-Dipole-Allowed Two-Photon Resonance in C60
复制标题
C60 中电偶极子允许的最低双光子共振的观测
DOI：
10.1021/jp9639096
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发表时间：
1997
期刊：
影响因子：
--
通讯作者：
Z. Kafafi
中科院分区：
文献类型：
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作者：
F. Strohkendl;T. J. Axenson;R. J. Larsen;L. Dalton;R. Hellwarth;Z. Kafafi
利用时间分辨简并四波混频（DFWM）技术，在0.74 - 1.7 μm的飞秒脉冲下，测量了CaF 2衬底上10 μm非晶C60薄膜的电子三阶非线性光学极化率张量cijkl（−ω，−ω）中所有非零元素的相位和振幅。在此范围内线性吸收小于1%。在DFWM中我们发现了一个单共振，其振幅和相位用双光子共振的洛伦兹模型很好地拟合到离基态2.7 ± 0.1eV的能级上，宽度为0.25eV。峰值双光子吸收系数为0.02 cm/MW，基本上与块状砷化镓的峰值相同，块状砷化镓是双光子吸收体中最强和最广泛研究的吸收体之一。我们的结果表明，只有一个双光子允许的跃迁低于3.4 eV（以及低于第一个单光子跃迁），这是一个明确的签名，这是从理论上预期的。理论将对称性Hg分配给这个最低的两张照片。
We use time-resolved degenerate four-wavemixing (DFWM) with femtosecond pulses in the wavelength range 0.74−1.7 μm to measure both phase and amplitude of all nonvanishing elements of the electronic third-order nonlinear optical susceptibility tensor cijkl(−ω,ω,ω,−ω) of a 10 μm amorphous C60 film on a CaF2 substrate. Linear absorption is found to be less than 1% in this range. We find a single resonance in DFWM, the amplitudes and phases of which are fit well by a Lorentzian model of a two-photon resonance to a level 2.7 ± 0.1 eV above the ground level, with width 0.25 eV. The peak two-photon absorption coefficient is 0.02 cm/MW, essentially the same peak value as for bulk gallium arsenide, one of the strongest and most widely studied of the two-photon absorbers. Our results show there is only one two-photon allowed transition below 3.4 eV (as well as below the first one-photon transition), an unambiguous signature which is expected from theory. Theory assigns the symmetry Hg to this lowest lying two-photo...