Multiphoton excitation and ionization by elliptically polarized, intense short laser pulses: Recognizing multielectron dynamics and doorway states in C{sub 60} vs Xe

Journal Article · Fri May 15 04:00:00 EDT 2009 · Physical Review. A

DOI:https://doi.org/10.1103/PHYSREVA.79.053414· OSTI ID:21304712

Shchatsinin, I; Ritze, H -H; Schulz, C P; Hertel, I V ^[1]

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1. Max Born Institute, Max-Born-Str. 2a, D-12489 Berlin-Adlershof (Germany)

Ionization and fragmentation of C{sub 60} fullerenes are studied by time-of-flight mass spectrometry, in elliptically polarized femtosecond laser fields at 797 nm of intensities I{sub 0}=(0.5-4.3)x10{sup 14} W cm{sup -2}. Xe atoms serve as a test case. We derive a qualitative theory describing such polarization studies. It turns out that polarization dependence can very sensitively distinguish single active electron (SAE) and multiple active electrons dynamics. In the case of Xe a clear signature of SAE dynamics is observed, with very pronounced changes in the ion yield as a function of ellipticity, indicative of N=5-8 and 18-22 photon processes for Xe{sup +} and Xe{sup 2+}, respectively. In contrast, only a moderate polarization dependence is observed in the C{sub 60} case, although at least 5 h{nu} photons at 797 nm are needed to generate C{sub 60}{sup +} and additional 11 for C{sub 60}{sup 2+}. At lower intensities, a moderate reduction in the ion yield for circular polarization establishes a two-photon SAE absorption process, connected with the key role of the lowest unoccupied molecular orbital (LUMO)+1(t{sub 1g}) as 'doorway state'. The absence of any polarization effect at 399 nm corroborates this finding. At high intensities enhanced fragmentation is observed, which is tentatively attributed to returning loops of electron trajectories by the combined action of the C{sub 60}{sup +} field and the circularly polarized laser field - in contrast to conventional wisdom that linear polarization should lead to an enhanced recolliding electron yield. No sign of a pronounced multiphoton polarization signature with five and more photons is seen for C{sub 60} which would be predicted by the SAE picture - although the slopes of the ion yield as a function of intensity are given by the corresponding power laws {proportional_to}I{sub 0}{sup N}. This is taken as clear evidence of multielectron dynamics after reaching the doorway state.

• OSTI ID: 21304712
• Journal Information: Physical Review. A, Journal Name: Physical Review. A Journal Issue: 5 Vol. 79; ISSN 1050-2947; ISSN PLRAAN
• Country of Publication: United States
• Language: English

Related Subjects

74 ATOMIC AND MOLECULAR PHYSICS
ELECTRON-MOLECULE COLLISIONS
ELECTRONS
EXCITATION
FULLERENES
LASER RADIATION
LASERS
MASS SPECTRA
MASS SPECTROSCOPY
MOLECULAR ORBITAL METHOD
MULTI-PHOTON PROCESSES
PHOTOIONIZATION
PHOTOLYSIS
PHOTON-MOLECULE COLLISIONS
PHOTONS
POLARIZATION
TIME-OF-FLIGHT METHOD
XENON IONS
YIELDS