Synchrotron radiation studies of gas phase molecules; from hydrogen to DNA sugars

This thesis summarises experimental results on the molecular spectroscopy
of gas phase molecules excited by synchrotron radiation in the VUV and soft
X-ray regions. We have used three different detection techniques, photon in-
duced fluorescence spectroscopy, photoionisation mass spectroscopy and near
edge X-ray absorption fine structure spectroscopy to study molecular deu-
terium, hydrogen sulphide, ammonia, methanol, pyridine, pyridazine, pyrim-
idine, pyrazine, s-triazine, and 2-deoxy-D-ribose, the last one also known as
the DNA sugar. Out of this variety of techniques and molecules we have
shown that: (1) high resolution dispersed fluorescence allows us to identify
vibrational and rotational bands in molecular deuterium, as well as to esti-
mate the predissociation probability of the same molecule [paper I]; (2) the
main species fluorescing after core excitation of methane, ammonia [paper
III], hydrogen sulphide [paper II], pyridine, pyrimidine and s-triazine is H
Balmer α, followed by fluorescence from ionised species, molecular bands and
Balmer β, γ , δ; (3) the Rydberg enhancement seen in fluorescence measure-
ments of water [Melero et al. PRL 96 (2006) 063003], corroborated later in
H2 S [paper II], N H3 [paper III] and C H4 [paper III] and postulated as gen-
eral behaviour for molecules formed by low-Z atoms, is also seen in larger
organic cyclic molecules, e.g. azabenzenes; (4) when dissociative ionisation
of pyridine, pyridazine, pyrimidine, pyrazine, s-triazine and 2-deoxy-D-ribose
occurs, concerted bond rearrangement and nuclear motion takes place as op-
posed to stepwise dissociation [papers V and VI].