Neutral dissociation and non Franck-Condon effects in valence excited N and O molecules
Författare
Summary, in English
Neutral photodissociation processes and non Franck-Condon effects in the N2 and O2 molecules
induced by excitation with synchrotron radiation photons have been studied in the 15-35 eV region.
Neutral dissociation processes have been studied by monitoring dispersed fluorescence from
excited N and O atoms. The excited atoms are created through excitations to members of the molecular
Rydberg series, which predissociate yielding excited atomic fragments. From comparison with
calculations performed using many-body perturbation theory it follows that predissociations of N2
Rydberg series are caused by a number of non-Rydberg doubly excited resonances whereas
predissociation of O2 Rydberg series occur after interaction with close-lying singly and doubly excited
valence states of the appropriate symmetry.
Photoelectron spectroscopy has been used to study photoionization of the N2 molecules to the
N2+ A 2Πu state and photoionization of the O2 molecules to the O2+ X 2Πg state. Dispersed fluorescence
emitted from the O2+ molecules has been measured to study the photoionization to the b 4Σ-g state of
O2+. All three photoionization channels exhibit strong non Franck-Condon effects in their experimental
vibrational branching ratios. In the case of the b 4Σ-g state of O2+, these effects seems to be originated
by the narrow 3σg σu shape resonance coupled to the 1πu πg channel. Conversely, the σu shape
resonance does not control the ionization to the O2+ X 2Πg and to the N2+ A 2Πu states. Photoionization
of the O2 πg electron is not fully explained by autoionization from known Rydberg series and valence
states, which suggest the existence of unknown process affecting this photoionization channel. On the
contrary, the Franck-Condon breakdown in the ionization to the N2+ A 2Πu state in the studied region is
attributed to autoionization from Rydberg and valence states of N2.
induced by excitation with synchrotron radiation photons have been studied in the 15-35 eV region.
Neutral dissociation processes have been studied by monitoring dispersed fluorescence from
excited N and O atoms. The excited atoms are created through excitations to members of the molecular
Rydberg series, which predissociate yielding excited atomic fragments. From comparison with
calculations performed using many-body perturbation theory it follows that predissociations of N2
Rydberg series are caused by a number of non-Rydberg doubly excited resonances whereas
predissociation of O2 Rydberg series occur after interaction with close-lying singly and doubly excited
valence states of the appropriate symmetry.
Photoelectron spectroscopy has been used to study photoionization of the N2 molecules to the
N2+ A 2Πu state and photoionization of the O2 molecules to the O2+ X 2Πg state. Dispersed fluorescence
emitted from the O2+ molecules has been measured to study the photoionization to the b 4Σ-g state of
O2+. All three photoionization channels exhibit strong non Franck-Condon effects in their experimental
vibrational branching ratios. In the case of the b 4Σ-g state of O2+, these effects seems to be originated
by the narrow 3σg σu shape resonance coupled to the 1πu πg channel. Conversely, the σu shape
resonance does not control the ionization to the O2+ X 2Πg and to the N2+ A 2Πu states. Photoionization
of the O2 πg electron is not fully explained by autoionization from known Rydberg series and valence
states, which suggest the existence of unknown process affecting this photoionization channel. On the
contrary, the Franck-Condon breakdown in the ionization to the N2+ A 2Πu state in the studied region is
attributed to autoionization from Rydberg and valence states of N2.
Publiceringsår
2001
Språk
Engelska
Dokumenttyp
Licentiatavhandling
Förlag
Stockholm: KTH, Physics
Ämne
- Electrical Engineering, Electronic Engineering, Information Engineering
Status
Published
Handledare
- Andrzej Karawajczyk
ISBN/ISSN/Övrigt
- Trita-FYS, ISSN 0280-316X ; 1073