Transcript tyler_troyl.ppt

The Electronic Spectroscopy of
the jet-cooled 1-Indanyl Radical
Tyler P. Troy
The University of Sydney
School of Chemistry
2009
The resonance stabilized radicals (RSRs)
• Slower reaction rates compared
to localized radicals
• Preferentially formed following
decomposition of stable species
benzyl radical
• Slower rates of dissociation
• Reach high concentrations
allowing for self-reaction OR
reaction with other RSRs
Reactions involving RSRs
Propargyl self-reaction
Melius J. A. et al.,Combust. Flame, 91, 1992
Phenylpropargyl from
phenyl + propargyl
Reilly N. J. et al., J. Am. Chem. Soc., 130, 10, 2008
Reilly N. J. et al., J. Am. Chem. Soc. submitted.
cis-vinyl propargyl radical
trans-vinyl propargyl radical
Astrochemical significance of the RSRs
Diffuse Interstellar Bands
Jenniskens P. et al., Ap.J., 183, 87, 1973
Unidentified Infrared Bands
F.C. Gillett et al., Ap.J., 183, 87, 1973
• Polycyclic Aromatic Hydrocarbons
• RSRs containing the benzylic
moiety exhibit visible transitions
dominated by the origin band
Titan
Cassini-Huygens
Possible Radical Intermediates to PAHs
Vereecken et al., J. Am. Chem. Soc., 124, 11, 2002
Possible Radical Intermediates to PAHs
Vereecken et al., J. Am. Chem. Soc., 124, 11, 2002
Experimental Details
TECHNIQUES
(REMPI-TOFMS)
Resonant-Enhanced
Multi-Photon Ionization –
Time of Flight Mass
Spectroscopy
(LIF)
Laser Induced
Fluorescence
(DF)
Dispersed
Fluorescence
SOURCE
Pulsed discharge nozzle
1.5 kV, 2.5 kΩ
Buffer Gas
LASER SYSTEMS
Excimer-pumped Lamba
Physik Dye Laser
(Excitation)
Argon, 4 bar
4th Harmonic (266nm)
from Nd:YAG Laser
Precursors
(Ionization)
Indene
Indan
Excitation spectra: R2C2PI of m/z=117
Excitation spectra: LIF vs R2C2PI
LIF – R2C2PI (m/z=117+m/z=115)
LIF
R2C2PI m/zR2C2PI
=115 +m/z
m/z=117
=117
=115
=133
Photo-ionization efficiency curve
Some possible carriers of m/z=117
Experimenting with precursors
NO RESONANT
SIGNAL
allyl benzene
3-FOLD INCREASE
RESONANT SIGNAL
indan
indene
Some possible carriers of m/z=117
Relative energies and IPs by DFT†
† B3LYP/6-311++G**
Dispersed fluorescence (DF)
experiment
0-0 pumping
simulation
Franck-Condon Factor
GS: DFT-B3LYP
ES: CAS(9,9)
BASIS: 6-311++G**
Conclusions and Future Work
• Assigned the species carrying m/z=117 from an indene/argon
discharge the 1-indanyl radical.
• Assigned most of the ground state frequencies of the 1-indanyl
radical.
• Found no coincidence between the 1-indanyl radical and the
Diffuse Interstellar Bands.
• Observed the formation of the 1-phenylpropargyl radical from
an indene/argon discharge and the formation of some species
carrying m/z=133
• Further research into the possible carrier of m/z=133.
• Consider other RSRs carrying the benzylic moiety
Nearly coincident with 4723 Å DIB
Conclusions and Future Work
• Assigned the species carrying m/z=117 from an indene/argon
discharge the 1-indanyl radical.
• Assigned most of the ground state frequencies of the 1-indanyl
radical.
• Found no coincidence between the 1-indanyl radical and the
Diffuse Interstellar Bands.
• Observed the formation of the 1-phenylpropargyl radical from
an indene/argon discharge and the formation of some species
carrying m/z=133
• Further research into the possible carrier of m/z=133.
• Consider other RSRs carrying the benzylic moiety
Acknowledgements
• My supervisor, Dr Timothy Schmidt
• Dr Masakazu Nakajima
• The laser spectroscopy group
• ARC (Project # DP0985767)
University of Sydney
UPA