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Study on the carbon fragment anions produced by femtosecond laser ablation of solid C60.

Production of the anions (negative ions) has been observed by femtosecond laser ablation (fsLA) of solid C(60) with a time-of-flight (TOF) mass spectrometer. In contrast to C(60)(+), production of C(60)(-) due to an electron capture is found very limited because of the small electron affinity of the C(60) molecule. Narrow TOF peaks of small carbon fragment anions C(n)(-) (n ≤ 23) suggest instantaneous production of the fragment anions through dissociative ionization of C(60). Production of the mono-hydrogenated carbon fragment anions C(n)H(-) has been observed and also the abrupt change in the yield of C(n)H(-) has been observed at n = 10, which is attributed to the structural change of the carbon fragments from a linear chain to a monocyclic ring. The results are found similar to those obtained for the carbon fragments produced by nanosecond laser ablation (nsLA) of solid C(60), which demonstrates that the thermalization in an ablation plasma washes away any difference in the nature of carbon fragments produced by fsLA and nsLA.