26
A. Palacios et al.
time evolution of both electron and proton distributions after the interaction with
ultrashort pulses.
2.1 Introduction
The success of the new generation of laser sources in providing intense femtosecond (1 fs = 10 −15 s) and attosecond (1 as = 10 −18 s) pulses opens the door to
manipulation and control of molecular electron dynamics. The last two decades
have witnessed a qualitative step forward on laser assisted applications in physics,
chemistry and biology [1–3]. First pump-probe experiments using 10–100 fs laser
pulses were able to retrieve information with atomic time and space resolutions. The
development of femtochemistry research, awarded with the Nobel Prize in Chemistry in 1999 [4], led to images at the time scale of nuclear motion allowing us to
unravel the dynamics of chemical bond breaking and formation and intramolecular
processes [2]. The more recent breakthroughs in x-ray free electron laser (XFEL)
sources that combine high peak power with few-fs pulses made it possible to explore an even wider variety of ultrafast phenomena [5–8]. In line with those, highharmonic generation (HHG) techniques soon made the attosecond science sprout
[9–12], with the commitment to achieve actual snapshots of electron motion, with
laser pulse durations down to hundreds of as. Today’s ultrafast scientific community
is rapidly improving experimental techniques leading to an increasing number of
studies in attosecond electron dynamics in atomic and molecular targets. Extensive
literature of the state-of-the-art attosecond science are given in [13–16]. The exceptional potential of the current laser technology thus challenges theoretical methods
to provide a solid groundwork to understand and interpret the mechanisms that are
responsible for a wealth of laser-induced processes. Despite the equally impressive
developments in supercomputing capabilities, substantial efforts are still necessary
to achieve full dimensional accurate theoretical descriptions of these processes in
multielectron atoms and molecules. The need for deep insights on the fundamental
physics that governs ultrafast laser-matter interactions make the simplest molecules
(H 2 , D 2 ) the ideal targets of study. The richness on the information that photoinduced excitation and ionization of these prototypical molecules provide is incomparable, being the only systems where the coupled motion of nuclei and electrons
(including electron correlation effects) can be tackled from ab initio quantum treatments. Detailed reviews on ultrafast dynamics in hydrogen molecules can be found
in [17–19].
The aim of this manuscript is to provide a survey on the latest experimental
and theoretical achievements on excitation and ionization of hydrogen molecules
by UV/XUV ultrashort laser pulses. We particularly focus on those processes that
can eventually lead to control of autoionization and multiphoton single-ionization
processes in molecules by acting at the few-fs and sub-fs time scales. We examine in
detail the mechanisms that are triggered at different frequencies by tuning the laser
parameters (pulse length, laser intensity, etc) and that indeed allow to manipulate the
A. Palacios et al.
time evolution of both electron and proton distributions after the interaction with
ultrashort pulses.
2.1 Introduction
The success of the new generation of laser sources in providing intense femtosecond (1 fs = 10 −15 s) and attosecond (1 as = 10 −18 s) pulses opens the door to
manipulation and control of molecular electron dynamics. The last two decades
have witnessed a qualitative step forward on laser assisted applications in physics,
chemistry and biology [1–3]. First pump-probe experiments using 10–100 fs laser
pulses were able to retrieve information with atomic time and space resolutions. The
development of femtochemistry research, awarded with the Nobel Prize in Chemistry in 1999 [4], led to images at the time scale of nuclear motion allowing us to
unravel the dynamics of chemical bond breaking and formation and intramolecular
processes [2]. The more recent breakthroughs in x-ray free electron laser (XFEL)
sources that combine high peak power with few-fs pulses made it possible to explore an even wider variety of ultrafast phenomena [5–8]. In line with those, highharmonic generation (HHG) techniques soon made the attosecond science sprout
[9–12], with the commitment to achieve actual snapshots of electron motion, with
laser pulse durations down to hundreds of as. Today’s ultrafast scientific community
is rapidly improving experimental techniques leading to an increasing number of
studies in attosecond electron dynamics in atomic and molecular targets. Extensive
literature of the state-of-the-art attosecond science are given in [13–16]. The exceptional potential of the current laser technology thus challenges theoretical methods
to provide a solid groundwork to understand and interpret the mechanisms that are
responsible for a wealth of laser-induced processes. Despite the equally impressive
developments in supercomputing capabilities, substantial efforts are still necessary
to achieve full dimensional accurate theoretical descriptions of these processes in
multielectron atoms and molecules. The need for deep insights on the fundamental
physics that governs ultrafast laser-matter interactions make the simplest molecules
(H 2 , D 2 ) the ideal targets of study. The richness on the information that photoinduced excitation and ionization of these prototypical molecules provide is incomparable, being the only systems where the coupled motion of nuclei and electrons
(including electron correlation effects) can be tackled from ab initio quantum treatments. Detailed reviews on ultrafast dynamics in hydrogen molecules can be found
in [17–19].
The aim of this manuscript is to provide a survey on the latest experimental
and theoretical achievements on excitation and ionization of hydrogen molecules
by UV/XUV ultrashort laser pulses. We particularly focus on those processes that
can eventually lead to control of autoionization and multiphoton single-ionization
processes in molecules by acting at the few-fs and sub-fs time scales. We examine in
detail the mechanisms that are triggered at different frequencies by tuning the laser
parameters (pulse length, laser intensity, etc) and that indeed allow to manipulate the