Picosecond time-resolved near-IR spectra of C60 excited states by pump-probe measurements using a probe beam based on broad-band optical parametric generation

Photophysical and Nonlinear Absorptive Optical Limiting Properties of [60]Fullerene Dimer and Poly[60]fullerene Polymer

“…The sample solutions for the measurements were carefully degassed through repeated (up to 14 cycles) freeze−pump−thaw. The transient absorption spectrum of C 60 in toluene was recorded for the purpose of calibration, and the spectrum is in excellent agreement with those already reported in the literature (Figure ) 11a. For the C 60 dimer, a toluene solution of 20 μM concentration was used in the measurement, which corresponds to an optical density at the excitation wavelength 355 nm of ∼1.0.…”

“…The efficient intersystem crossing produces a high population of the excited triplet state. Because the triplet−triplet transient absorption cross sections are higher than the ground-state absorption cross sections, , C 60 in room-temperature solution exhibits excellent nonlinear absorptive optical limiting properties. − In fact, C 60 is actively investigated as one of the best broad-band optical limiters for potential laser power limiting and optical switching applications. , Similar excited-state properties have been observed for C 60 derivatives. − ,,,− For example, it has been shown that the excited-state properties of different methano-C 60 and pyrrolidino-C 60 derivatives are rather similar. ,,,, The derivatives are more fluorescent than the parent C 60 , with fluorescence yields of the derivatives being larger by approximately a factor of 3 and fluorescence lifetimes being longer by approximately 25% (1.4−1.6 ns for the derivatives vs 1.2 ns for C 60 ). , The intersystem crossing continues to be the dominating excited-singlet-state decay pathway in the C 60 derivatives, again with unity intersystem yields according to results from singlet molecular oxygen generation measurements. ,, The triplet−triplet transient absorption spectra of the C 60 derivatives have spectral profiles similar to that of the parent C 60 , but the spectra of the derivatives are slightly blue-shifted and have lower absorption cross sections. ,, However, the nonlinear absorptive properties of the C 60 derivatives as measured by optical limiting responses toward a nanosecond pulsed laser at 532 nm are only marginally different from those of the parent C 60 in room-temperature solutions. ,− …”

Time-resolved photoelectron spectroscopy of low-energy excitations of 4×4 C60/Cu(111)

“…This is faster than the laser pulse duration in the current work, and thus only the lowest excited singlet state needs to be considered in figure 1.3. The lowest singlet state cannot decay to the ground state by means of electric dipole radiation, and it is nearly in resonance with a triplet state, into which it can relax by means of spin orbit interaction [65]. Kao and coworkers [66] reported that the singlet state almost exclusively decays into a triplet state.…”

“…The corresponding decay rate matched the formation rate of the lowest triplet state. For isolated C 60 at room temperature Koishi and coworkers [65] determined the lifetime of the singlet exciton to be 1 ns and they showed that the lowest triplet state is populated by intersystem crossing from the lowest singlet state.…”

An overview of fullerene chemistry

“…The FTIR absorptions for C7o appear at 1132, 795, 674, 642 and 458cm -1. Picosecond time-resolved near-IR spectra obtained by pump-probe measurement showed singlet and triplet excited state absorption for C6o in the region 700-1300 nm (Watanabe et al 1996).…”