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Resonant multi-photon ionisation studies of high-energy states in small molecules
KTH, School of Engineering Sciences (SCI), Physics, Atomic and Molecular Physics.
2005 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

This thesis describes separate studies of high-energy Rydberg and ion-pair states in small molecules using resonant multi-photon ionisation spectroscopy.

* OODR/REMPI study of ungerade Rydberg states in O2

The energy region between 75000 and 99900 cm-1 of O2 has been studied using optical-optical double resonance (OODR) with resonance enhanced multi-photon ionisation (REMPI). Three-photon excitation via single rotational levels of the b(1Σ+g ) valence state was used to study np (n=3–10) and nf (n=4–9) Rydberg states converging on O2+X(2Π1/2,g) and X(2Π3/2,g). The excitation pathway picks out non-predissociated states that are singlet in the (Λ,S) coupling scheme – suitable for np states for n ≥8, or are linear combinations of equal weight of singlet and triplet-spin states in the (Ω,ω) coupling scheme which was found to be suitable for nf states for all values of n.

* OTR/RI study of Rydberg and ion-pair states in I2

Optical triple resonance (OTR) together with resonance ionisation (RI) has been used to study the ungerade manifold of molecular iodine between 57000 and 73000 cm-1 via the E 0g+(3P2) ion-pair state. Two 6s Rydberg states with 0 +u symmetry based on excited states of the ion core have been observed.

During this study we also observed electric-field-induced mixing of nearly isoenergetic rovibrational levels of the E0gP+(3P2) and D0u+(3P2) ion-pair states. Detectable mixing with an applied field of 1kV/cm occurs over a range of energy level separations of ≤0.3 cm-1.

* (2+1)and (3+1) REMPI study of pyrrole (C4H5N) The two- and three-photon REMPI spectra of Rydberg states of pyrrole (C4H5N) have been recorded using circularly and linearly polarised light. The spectra were compared to the single-photon absorption spectrum of pyrrole and a similar study of furan (C4H4O). Although the ionisation spectra of pyrrole were considerably weaker than corresponding furan spectra, a strong propensity for excitation of d series with two photons and p and f series with three photons was observed for both molecules. The totally symmetric nd-Rydberg series associated with the first ionisation energy, [A2]nd;A1, was identified from n=3 to n=15 and extrapolated to obtain IE1.

Place, publisher, year, edition, pages
Stockholm: KTH , 2005. , viii, 56 p.
Series
Trita-FYS, ISSN 0280-316X ; 2005:36
National Category
Physical Sciences
Identifiers
URN: urn:nbn:se:kth:diva-409ISBN: 91-7178-112-9 (print)OAI: oai:DiVA.org:kth-409DiVA: diva2:10682
Public defence
2005-09-23, Sal FA32, AlbaNova, Roslagstullsbacken 21, Stockholm, 10:00
Opponent
Supervisors
Note
QC 20101006Available from: 2005-09-13 Created: 2005-09-13 Last updated: 2010-10-06Bibliographically approved
List of papers
1. An optical-optical double-resonance study of the Rydberg states of O-2. II. The np and nf (ungerade) states excited via single-rotational levels of the b (1)Sigma(+)(0g) valence state
Open this publication in new window or tab >>An optical-optical double-resonance study of the Rydberg states of O-2. II. The np and nf (ungerade) states excited via single-rotational levels of the b (1)Sigma(+)(0g) valence state
2003 (English)In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 118, no 19, 8791-8796 p.Article in journal (Refereed) Published
Abstract [en]

The np (n=3-10) and nf (n=4-9) Rydberg states of O-2 converging on O-2+ X (2)Pi(1/2,g) and X (2)Pi(3/2g) have been studied between 75 000 and 99 900 cm-1 using optical-optical double resonance with multiphoton ionization. Three-photon excitation from single rotational levels of the initially excited b (1)Sigma(0g)(+) valence state was used to access these states. The nf states show a strong tendency towards (Omega,omega) coupling for all values of n, whereas the np states appear to be best described by (Lambda,S) coupling for nless than or equal to8. The intensities of some of the 5f bands are anomalously high due to accidental resonances with the 3s d (1)Pi(1g) Rydberg state at the two-photon level.

Keyword
multiphoton-ionization spectroscopy, indirect predissociation, identification, photoionization, spectrum, molecule, o2
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-6073 (URN)10.1063/1.1566949 (DOI)000182603000027 ()
Note
QC 20101006Available from: 2005-09-13 Created: 2005-09-13 Last updated: 2010-10-06Bibliographically approved
2. Electric-field-induced g/u mixing of the E0(3P2) and D0(3P2) ion-pair states of jet-cooled I2 observed using optical triple resonance
Open this publication in new window or tab >>Electric-field-induced g/u mixing of the E0(3P2) and D0(3P2) ion-pair states of jet-cooled I2 observed using optical triple resonance
2004 (English)In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 120, no 6, 2740-2745 p.Article in journal (Refereed) Published
Abstract [en]

Electric-field-induced electronic state g/u mixing of nearly isoenergetic rovibrational levels of the E0(g)(+)(P-3(2)) and D0(u)(+)(P-3(2)) ion-pair states of I-2 has been observed using optical triple resonance combined with resonance ionization. Detectable mixing with applied fields of 1 kV/cm occurs over a range of energy level separations of less than or equal to0.3 cm(-1).

Keyword
energy-transfer, diatomic molecule, spectroscopy, transitions, ionization, iodine, collisions, constants, system, i2
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-6074 (URN)10.1063/1.1637590 (DOI)000188880500022 ()2-s2.0-1542426550 (Scopus ID)
Note
QC 20101006Available from: 2005-09-13 Created: 2005-09-13 Last updated: 2010-10-06Bibliographically approved
3. Observation of a new high-energy, shallow-bound Rydberg state in I-2 by optical triple resonance
Open this publication in new window or tab >>Observation of a new high-energy, shallow-bound Rydberg state in I-2 by optical triple resonance
2005 (English)In: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 412, no 1-3, 110-115 p.Article in journal (Refereed) Published
Abstract [en]

A new 0(u)(+)6s Rydberg state built on an excited ionic core of I-2 has been observed by optical triple resonance via the B(O-u(+)) valence and EOg+ (P-3(2)) ion-pair states with ionization detection. A vibrational progression, v = 0-27, was observed for selected rotational levels and molecular constants are presented. The Rydberg state is weakly bound and was determined to have an internuclear separation of 4.500 +/- 0.003 angstrom.

Keyword
ion-pair states, photoelectron-spectra, absorption-spectrum, field-ionization, iodine molecule, spectroscopy, excitation, system, i2
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-6075 (URN)10.1016/j.cplett.2005.06.095 (DOI)000231207400022 ()2-s2.0-23144448251 (Scopus ID)
Note

QC 20101006

Available from: 2005-09-13 Created: 2005-09-13 Last updated: 2012-10-10Bibliographically approved
4. Observation of a substantially-bound excited-core Rydberg state in I2 by optical triple resonance
Open this publication in new window or tab >>Observation of a substantially-bound excited-core Rydberg state in I2 by optical triple resonance
2005 (English)In: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 416, no 1-3, 64-69 p.Article in journal (Refereed) Published
Abstract [en]

A substantially-bound (D-e similar to 7000 cm(-1), R-e similar to 3.1 angstrom, T-e similar to 60 546 cm(-1)) 6s Rydberg state Of I-2 with 0(u)(+) symmetry based on the lowest excited state of the ion core, previously labelled a (4 Sigma(u,)(1/2)(-)), has been identified using optical triple resonance via the B(0(u)(+)) and E0(g)(+)(P-3(2)) states together with resonance ionization. The interactions with ground-core Rydberg states that the new state undergoes and the reasons why it is observed in the resonance ionization spectrum via the E0(g)(+)(P-3(2)) state, whilst the A[(2)Pi(u,1/2)](c); 6s0(u)(+) state is not, are explained in terms of its electronic configuration.

Keyword
ion-pair states, photoelectron-spectra, field-ionization, band system, iodine, spectroscopy, energy
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-6076 (URN)10.1016/j.cplett.2005.09.029 (DOI)000233687000013 ()2-s2.0-33644523061 (Scopus ID)
Note
Uppdaterad från submitted till published: 20101006 QC 20101006Available from: 2005-09-13 Created: 2005-09-13 Last updated: 2010-10-06Bibliographically approved

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