Fragmentation cross sections of fullerene cations have been measured as a function of collision energy under single collision conditions. The ions are produced by laser desorption from a C 60 /C 70 substrate. Collision products are analyzed with a linear time of flight mass spectrometer. The collision energy ranges from 5 eV up to more than 150 eV in the center of mass reference frame. A combination of molecular dynamics calculations and statistical RRKM theory has been applied to help understand the nature of the fragmentation dynamics. The results of collisions using different fullerenes as projectiles ͑C 56 ϩ , C 58 ϩ , C 60 ϩ , C 70 ϩ ͒ as well as collisions with a range of target gases ͑Ne, Ar, O 2 , CO 2 , ͑CH 2 ͒ 3 , C 3 H 6 , SF 6 ͒ give additional insight into the fragmentation mechanisms. The energy dependence of the fragmentation cross sections can be used to identify exothermic reactions between projectile and target as is shown for the case of molecular oxygen.

Abstract.Photo-ionisation and -fragmentation of C6o by 15 ns excimer laser pulses at 308 nm and 193 nm as well as 0.8 ps laser pulses at 193 nm has been studied with reflectron time-of-flight mass spectrometry. The initial fragmentation process is ejection of C,,, n > 2, as opposed to successive Cz evaporation. Studies of the relative intensities of metastable fragmentation processes compared with direct fragmentation provide new insight into the fragmentation mechanism and provide a thermometer for the internal energy of C~-o prior to fragmentation. The proposed mechanism is in agreement with measurements of the fragment ion kinetic energies. The results are compared with molecular dynamics simulations.

Third-harmonic generation from solid samples of carbon nanotubes has been studied experimentally, using ultrashort pulses generated by a Cr:Forsterite laser, at a wavelength of 1250 nm. The results show an unusual nonperturbative behavior of the third-harmonic yield, for relatively low input laser fields, of ∼1010 W/cm2. This strong nonlinearity of the laser interaction with carbon nanoubes is also confirmed theoretically, in a full quantum-mechanical theory for harmonics generation from a single-walled carbon nanotube.

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A method of combined thin-film deposition, electron beam lithography, and ion milling is presented for the fabrication of gold and silver nanostructures. The flexibility of lithographical processes for the variation of geometric parameters is combined with three-dimensional control over the surface evolution. Depending on the etching angle, different shapes ranging from cones over rods to cups can be achieved. These size- and shape-tunable structures present a toolbox for nano-optical investigations. As an example, optical properties of systematically varying structures are examined in a parabolic mirror confocal microscope.