pulse (ArF excimer laser, 193 nm, 6.4 eV) directly into the high vacuum (5 x 10 6 torr). After 30-40 (is, the desorbed species are extracted by a pulsed field and mass-analyzed according to their time of flight within the mass spectrometer instrument. The enhanced concentration of Cg4 relative to C60 is shown in Fig. 5.7, where the LDMS instrument is operating in the positive ion mode, using an ArF excimer laser at 193 nm, and ~1.5 mJ/cm2 power level for the desorption of the molecular species. In the hotter region, the concentration of higher-mass fullerenes on the quartz rod is seen to be greater.

As another example of separation by sublimation in a temperature gradient, the enhanced concentration of the metallofullerenes [email protected] and [email protected] relative to C70 is shown in Fig. 5.8, where LDMS data are shown for a 10-mm-long ribbon of fullerenes deposited along the temperature gradient. During the first 20 mm (not shown), a gradual increase

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