5 research outputs found
Supplement 1: Energy-dependent photoemission delays from noble metal surfaces by attosecond interferometry
Originally published in Optica on 20 May 2015 (optica-2-5-405
Ultrafast Relaxation Dynamics of the Ethylene Cation C<sub>2</sub>H<sub>4</sub><sup>+</sup>
We
present a combined experimental and computational study of the
relaxation dynamics of the ethylene cation. In the experiment, we
apply an extreme-ultraviolet-pump/infrared-probe scheme that permits
us to resolve time scales on the order of 10 fs. The photoionization
of ethylene followed by an infrared (IR) probe pulse leads to a rich
structure in the fragment ion yields reflecting the fast response
of the molecule and its nuclei. The temporal resolution of our setup
enables us to pinpoint an upper bound of the previously defined ethylene–ethylidene
isomerization time to 30 ± 3 fs. Time-dependent density functional
based trajectory surface hopping simulations show that internal relaxation
between the first excited states and the ground state occurs via three
different conical intersections. This relaxation unfolds on femtosecond
time scales and can be probed by ultrashort IR pulses. Through this
probe mechanism, we demonstrate a route to optical control of the
important dissociation pathways leading to separation of H or H<sub>2</sub>
Few-Femtosecond C<sub>2</sub>H<sub>4</sub><sup>+</sup> Internal Relaxation Dynamics Accessed by Selective Excitation
Dissociation
of the ethylene cation is a prototypical multistep
pathway in which the exact mechanisms leading to internal energy conversions
are not fully known. For example, it is still unclear how the energy
is exactly redistributed among the internal modes and which step is
rate-determining. Here we use few-femtosecond extreme-ultraviolet
pulses of tunable energy to excite a different superposition of the
four lowest states of C2H4+ and probe
the subsequent fast relaxation with a short infrared pulse. Our results
demonstrate that the infrared pulse photoexcites the cationic ground
state (GS) to higher excited states, producing a hot GS upon relaxation,
which enhances the fragmentation yield. As the photoexcitation probability
of the GS strongly depends on the molecular geometry, the probing
by the IR pulse provides information about the ultrafast excited-state
dynamics and the type of conical intersection (planar or twisted)
involved in the first 20 fs of the nonradiative relaxation
Ultrafast Relaxation Dynamics of the Ethylene Cation C<sub>2</sub>H<sub>4</sub><sup>+</sup>
We
present a combined experimental and computational study of the
relaxation dynamics of the ethylene cation. In the experiment, we
apply an extreme-ultraviolet-pump/infrared-probe scheme that permits
us to resolve time scales on the order of 10 fs. The photoionization
of ethylene followed by an infrared (IR) probe pulse leads to a rich
structure in the fragment ion yields reflecting the fast response
of the molecule and its nuclei. The temporal resolution of our setup
enables us to pinpoint an upper bound of the previously defined ethylene–ethylidene
isomerization time to 30 ± 3 fs. Time-dependent density functional
based trajectory surface hopping simulations show that internal relaxation
between the first excited states and the ground state occurs via three
different conical intersections. This relaxation unfolds on femtosecond
time scales and can be probed by ultrashort IR pulses. Through this
probe mechanism, we demonstrate a route to optical control of the
important dissociation pathways leading to separation of H or H<sub>2</sub>