Anisotropic hot electron emission from fullerenes

Abstract

Photoelectron spectra for fullerenes C(60) and C(70) ionized using 800 nm laser pulses with pulse durations from 120 to 1000 fs show thermal electron kinetic energy distributions but they also exhibit angular anisotropy with respect to the laser light polarization. The effective temperature of electrons, measured along the laser polarization direction, is significantly higher than in the perpendicular direction. We explain this observation by considering that the emission of the thermal electrons is uncorrelated with the phase of the laser pulse, unlike directly ionized electrons, and, depending on the time of emission, they may experience an additional "kick" from the vector potential of the laser field when they are emitted from the molecule.

Probing excited electronic states and ionisation mechanisms of fullerenes

“…[12][13][14] Similar features are seen in fs laser PES of fullerenes 15,16 superimposed on a background of thermal electrons. 17,18 We will discuss the interesting nature of these states in fullerenes and the reason for their prominence in the PES. 16…”

Transition from SAMO to Rydberg State Ionization in C60 in Femtosecond Laser Fields

“…16,18 In fs laser fields (down to tens of fs), prominent peak structures can be observed superimposed on a “thermal” background. 19,20 Within time scales of about 100 fs, the excitation energy mostly remains in electronic degrees of freedom, yielding emitted photoelectrons with a much higher effective temperature compared to those obtained in ps laser fields, where significant energy can be transferred to vibrations. 14,19,21 The nature of electron emission has been shown to depend on laser fluence for femtosecond pulses at moderate intensities.…”

Super-atom molecular orbital excited states of fullerenes

“…The laser light was linearly polarized with the electric vector aligned in the vertical direction. In order to obtain a good signal to noise ratio for the SAMO peaks while minimizing the background contribution due to thermoelectronic ionization [16], the laser intensity typically was within the range 10 11 -10 12 W cm −2 .…”