Open AccessTransition from SAMO to Rydberg State Ionization in C60 in Femtosecond Laser Fields
Author(s) -
H. Li,
Benoît Mignolet,
Zhe Wang,
K. J. Betsch,
K. D. Carnes,
I. BenItzhak,
C. L. Cocke,
Françoise Remacle,
Matthias F. Kling
Publication year - 2016
Publication title -
the journal of physical chemistry letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.563
H-Index - 203
ISSN - 1948-7185
DOI - 10.1021/acs.jpclett.6b02139
Subject(s) - ionization , atomic physics , rydberg formula , femtosecond , rydberg state , laser , chemistry , ionization energy , kinetic energy , spectral line , physics , ion , optics , organic chemistry , quantum mechanics , astronomy
The transition between two distinct ionization mechanisms in femtosecond laser fields at 785 nm is observed for C 60 molecules. The transition occurs in the investigated intensity range from 3 to 20 TW/cm 2 and is visualized in electron kinetic energy spectra below the one-photon energy (1.5 eV) obtained via velocity map imaging. Assignment of several observed broad spectral peaks to ionization from superatom molecular orbitals (SAMOs) and Rydberg states is based on time-dependent density functional theory simulations. We find that ionization from SAMOs dominates the spectra for intensities below 5 TW/cm 2 . As the intensity increases, Rydberg state ionization exceeds the prominence of SAMOs. Using short laser pulses (20 fs) allowed uncovering of distinct six-lobe photoelectron angular distributions with kinetic energies just above the threshold (below 0.2 eV), which we interpret as over-the-barrier ionization of shallow f-Rydberg states in C 60 .