biochromophore ions and the role of microenvironments such as water or nearby
charge sites. The chapter ends by touching upon possible future directions for the
field. In the next chapter, Wyer introduces the experimental techniques used for
performing gas-phase spectroscopy of ions with emphasis on ion storage rings and
other home-built ion beam set-ups as these are less well described in the literature.
It is certainly true that no experiment is perfect, and Wyer discusses the advantages
and disadvantages with different set-ups, differences between positive and negative
ions and importantly what to be cautious about when interpreting experimental
results. In the next chapter by Rubio and Wanko, theoretical methods that are
commonly employed to describe these rather big systems are presented. Also
here the methods are carefully evaluated and their performances relative to each
other are discussed. The subsequent chapters deal with actual biochromophores and
their photophysics. The chapter by Andersen and Bochenkova gives an overview of
the GFP chromophore anion and its absorption spectrum; this spectrum from 2001
was the first to be obtained for an isolated biochromophore ion. The authors discuss
the competition between electron photodetachment and internal conversion, which
is an issue that needs to be considered for anions whose detachment energies are
within the absorption band. The next chapter by Brøndsted Nielsen deals with the
detection of light emitted from photoexcited chromophore ions (dyes), which is
even harder experimentally than obtaining an absorption spectrum. Still fluorescence spectroscopy has proven to be a very strong tool for monitoring structures of
isolated biomolecular ions. Wyer and Brøndsted Nielsen summarise in the following chapter the increasing amount of data on porphyrin and heme ions and their
complexes with amino acids and NO and compare results with protein spectra. Also
two-laser experiments are discussed allowing one to record spectra of long-lived
photoexcited ions. Spectra of whole proteins are presented in the next chapter by
Antoine and Dugourd, where either heme or aromatic amino acid residues are the
absorbing species. The authors demonstrate the importance of the charge state in
obtaining action spectra, and from two-laser experiments they nicely succeed in
performing spectroscopy on radical species. Dedonder, Fe ´raud, and Jouvet provide
a comprehensive review of the field of spectroscopy of protonated amino acids and
small peptide ions, both at room temperature and at low temperature, with emphasis
on the fast dissociation channels that are operative when the ions are electronically
excited and that compete with internal conversion to the electronic ground state;
their relative importance is measured from photodissociation of the ions in an
electric field. The number of fragments formed in a dissociation process is found
from coincidence experiments considering momentum conservation. Timescales
for the deexcitation processes are established from femtosecond pump-probe laser
experiments. Their work nicely demonstrates how experimental results and theoretical ones go hand in hand in obtaining the deepest level of understanding. DNA
and RNA nucleotides and oligonucleotides are the focus of the chapter by Weber,
Marcum, and Brøndsted Nielsen who in detail discuss UV-induced fragmentation
channels, timescales for dissociation after photoexcitation and whether dissociation
is statistical or nonstatistical, and finally electronic spectra (both absorption and
photoelectron spectra). In this chapter the complex role of multiple light absorbing
vi
Preface
charge sites. The chapter ends by touching upon possible future directions for the
field. In the next chapter, Wyer introduces the experimental techniques used for
performing gas-phase spectroscopy of ions with emphasis on ion storage rings and
other home-built ion beam set-ups as these are less well described in the literature.
It is certainly true that no experiment is perfect, and Wyer discusses the advantages
and disadvantages with different set-ups, differences between positive and negative
ions and importantly what to be cautious about when interpreting experimental
results. In the next chapter by Rubio and Wanko, theoretical methods that are
commonly employed to describe these rather big systems are presented. Also
here the methods are carefully evaluated and their performances relative to each
other are discussed. The subsequent chapters deal with actual biochromophores and
their photophysics. The chapter by Andersen and Bochenkova gives an overview of
the GFP chromophore anion and its absorption spectrum; this spectrum from 2001
was the first to be obtained for an isolated biochromophore ion. The authors discuss
the competition between electron photodetachment and internal conversion, which
is an issue that needs to be considered for anions whose detachment energies are
within the absorption band. The next chapter by Brøndsted Nielsen deals with the
detection of light emitted from photoexcited chromophore ions (dyes), which is
even harder experimentally than obtaining an absorption spectrum. Still fluorescence spectroscopy has proven to be a very strong tool for monitoring structures of
isolated biomolecular ions. Wyer and Brøndsted Nielsen summarise in the following chapter the increasing amount of data on porphyrin and heme ions and their
complexes with amino acids and NO and compare results with protein spectra. Also
two-laser experiments are discussed allowing one to record spectra of long-lived
photoexcited ions. Spectra of whole proteins are presented in the next chapter by
Antoine and Dugourd, where either heme or aromatic amino acid residues are the
absorbing species. The authors demonstrate the importance of the charge state in
obtaining action spectra, and from two-laser experiments they nicely succeed in
performing spectroscopy on radical species. Dedonder, Fe ´raud, and Jouvet provide
a comprehensive review of the field of spectroscopy of protonated amino acids and
small peptide ions, both at room temperature and at low temperature, with emphasis
on the fast dissociation channels that are operative when the ions are electronically
excited and that compete with internal conversion to the electronic ground state;
their relative importance is measured from photodissociation of the ions in an
electric field. The number of fragments formed in a dissociation process is found
from coincidence experiments considering momentum conservation. Timescales
for the deexcitation processes are established from femtosecond pump-probe laser
experiments. Their work nicely demonstrates how experimental results and theoretical ones go hand in hand in obtaining the deepest level of understanding. DNA
and RNA nucleotides and oligonucleotides are the focus of the chapter by Weber,
Marcum, and Brøndsted Nielsen who in detail discuss UV-induced fragmentation
channels, timescales for dissociation after photoexcitation and whether dissociation
is statistical or nonstatistical, and finally electronic spectra (both absorption and
photoelectron spectra). In this chapter the complex role of multiple light absorbing
vi
Preface