Ultrafast degenerate pump-probe experiments performed on a free standing filmof double walled carbon nanotubes near the first metallic transition energy ofouter tube show ultrafast ($97 fs$) photobleaching followed by a photo-inducedabsorption with a slow relaxation of $1.8 ps$. Femtosecond closed and openaperture z-scan experiments carried out at the same excitation energy showsaturation absorption and negative cubic nonlinearity. From these measurements,real and imaginary part of the third order nonlinear susceptibility areestimated to be Re($\chi^{(3)}) \sim -2.2 \times 10 ^{-9} esu$ andIm($\chi^{(3)}) \sim 1.1 \times 10 ^{-11} esu$.
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机译：在外管的第一个金属跃迁能附近的双壁碳纳米管的独立膜上进行的超快简并泵浦探针实验显示，超快（$ 97 fs $）的光漂白，随后是光诱导的吸收，缓慢弛豫为$ 1.8 ps $。在相同激发能量下进行的飞秒闭合和开孔z扫描实验显示了饱和吸收和负立方非线性。根据这些测量，估计三阶非线性磁化率的实部和虚部分别为Re（$ \ chi ^ {（3）}）\ sim -2.2 \ times 10 ^ {-9} esu $和Im（$ chi \ { （3）}）\ sim 1.1 \ times 10 ^ {-11} esu $。
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