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Measurement of Ultrafast Vibrational Coherences in Polyatomic Radical Cations with Strong-Field Adiabatic Ionization
Published on: August 6, 2018
Large molecules reveal a linear length scaling for double photoionization
T Hartman1, P N Juranić, K Collins
1Synchrotron Radiation Center, University of Wisconsin-Madison, Stoughton, Wisconsin 53589, USA.
Physical Review Letters
|February 14, 2012
Summary
The double photoionization of molecules like benzene shows a surprising similarity to helium. Their double-to-single ionization ratio scales linearly with molecular length, impacting biomolecular radiation damage.
Area of Science:
- Atomic and Molecular Physics
- Chemical Physics
- Radiation Physics
Background:
- Double photoionization (DPI) is a fundamental process in atomic and molecular physics.
- Understanding DPI in larger molecules is crucial for applications in radiation biology and materials science.
- Previous studies have focused on atomic systems and smaller molecules, with limited data on polycyclic aromatic hydrocarbons (PAHs).
Purpose of the Study:
- To investigate the ratio of doubly to singly charged parent ions for benzene, naphthalene, anthracene, and pentacene.
- To compare the DPI behavior of these molecules with that of helium.
- To explore the relationship between molecular length and DPI probability.
Main Methods:
- Utilizing monochromatized synchrotron radiation.
- Measuring ion yield ratios for benzene, naphthalene, anthracene, and pentacene.
- Scanning photon energies up to 30 eV above the ionization threshold.
Main Results:
- A striking similarity was observed between the doubly to singly charged ion ratio for the studied molecules and helium.
- The ratio of doubly charged to all parent ions scaled linearly with the molecular length of the investigated PAHs.
- A high double-to-single ionization ratio indicates a significant probability for double photoionization.
Conclusions:
- The DPI process in larger PAHs exhibits universal characteristics, similar to atomic systems like helium.
- Molecular length is a key factor governing the relative double photoionization probability in these systems.
- Molecules with high DPI probabilities are significant sources of low-energy electrons, potentially contributing to radiation damage in biological molecules.
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