XUV excitation followed by ultrafast non-adiabatic relaxation in PAH molecules as a femto-astrochemistry experiment.
Highly excited molecular species are at play in the chemistry of interstellar media and are involved in the creation of radiation damage in a biological tissue. Recently developed ultrashort extreme ultraviolet light sources offer the high excitation energies and ultrafast time-resolution required for probing the dynamics of highly excited molecular states on femtosecond (fs) (1 fs=10(-15) s) and even attosecond (as) (1 as=10(-18) s) timescales. Here we show that polycyclic aromatic hydrocarbons (PAHs) undergo ultrafast relaxation on a few tens of femtoseconds timescales, involving an interplay between the electronic and vibrational degrees of freedom. Our work reveals a general property of excited radical PAHs that can help to elucidate the assignment of diffuse interstellar absorption bands in astrochemistry, and provides a benchmark for the manner in which coupled electronic and nuclear dynamics determines reaction pathways in large molecules following extreme ultraviolet excitation.
Institut Lumière Matière, Université Lyon 1, CNRS, UMR 5306, 10 rue Ada Byron, 69622 Villeurbanne Cedex, France.
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Marciniak
Institut Lumière Matière, Université Lyon 1, CNRS, UMR 5306, 10 rue Ada Byron, 69622 Villeurbanne Cedex, France.
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Despré
Institut Lumière Matière, Université Lyon 1, CNRS, UMR 5306, 10 rue Ada Byron, 69622 Villeurbanne Cedex, France.
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Barillot
Max-Born-Institut, Max Born Strasse 2A, D-12489 Berlin, Germany.
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Rouzée
Max-Born-Institut, Max Born Strasse 2A, D-12489 Berlin, Germany.
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Galbraith
Max-Born-Institut, Max Born Strasse 2A, D-12489 Berlin, Germany.
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Klei
Max-Born-Institut, Max Born Strasse 2A, D-12489 Berlin, Germany.
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Yang
Max-Born-Institut, Max Born Strasse 2A, D-12489 Berlin, Germany.
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Smeenk
Institut Lumière Matière, Université Lyon 1, CNRS, UMR 5306, 10 rue Ada Byron, 69622 Villeurbanne Cedex, France.
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Loriot
School of Chemistry, University of Hyderabad, Hyderabad 500 046, India.
S Nagaprasad
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Reddy
Leiden Observatory, Leiden University, PO Box 9513, NL-2300RA Leiden, The Netherlands.
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Tielens
School of Chemistry, University of Hyderabad, Hyderabad 500 046, India.
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Mahapatra
Theoretische Chemie, PCI, Universität Heidelberg, Im Neuenheimer Feld 229, D-69120 Heidelberg, Germany.
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Kuleff
Max-Born-Institut, Max Born Strasse 2A, D-12489 Berlin, Germany.
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Vrakking
Institut Lumière Matière, Université Lyon 1, CNRS, UMR 5306, 10 rue Ada Byron, 69622 Villeurbanne Cedex, France.
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