Synthesis of C₆₀ Polymer by Free Electron Laser Irradiation with Tunable Wavelength

Abstract

The harmonics of free electron laser (FEL) were irradiated to the surfaces of compressed C₆₀ and/or mixture of C₆₀ and I₂ in the vacuum. After the irradiation of FEL with the typical wavelength, 450 nm or 345 nm, the Raman peak of Ag(2)-derived vibration mode of C₆₀ shifted to the lower energy side. This result suggested that polymerization reactions of C₆₀ proceeded. The largest peak shift, ca. 10 cm⁻¹ was obtained in the mixture powder irradiated by 345 nm irradiation. The decrease of the lattice parameter was confirmed by XRD analyses revealed that inter-molecular combinations took places. Furthermore the change of the crystal structure was closely studied by changing the wavelength of FEL in the range of 350–600 nm. The obtained results demonstrated that three-dimensional polymerization of C₆₀ was effectively promoted by FEL irradiation and/or especially the effect of the photon-assisted hole-doping from iodine atoms to C₆₀ molecules.

Keywords:

• Ag(2) mode
• C₆₀ polymer
• Free Electron Laser (FEL)
• Raman
• XRD

Acknowledgments

This work is partly supported by the “Academic Frontier” Project for Private Universities: matching fund subsidy from MEXT, 2000–2007. The authors would like to thank the stuffs of Laboratory for Electron Beam Research and Application of Nihon University for their helps of FEL operations.