69th International Symposiumon Molecular Spectroscopy

Consistent Assignment of the Vibrations of

Monohalosubstituted BenzenesJoe P. Harris, Anna Andrejeva, William D. Tuttle, Timothy G.

WrightSchool of Chemistry, University of Nottingham, UKIgor Pugliesi, Christian Schriever

Fakultät für Physik, Ludwig-Maximilians-Universität, München

Notation schemes for substituted benzenes

Introduction - Existing schemes

M notation - Mass trends - G-W Notation

Experiments

- Previous studies - Fluorobenzene - Fluorobenzene-d5

Conclusions - Future work

• Wilson notation

• Mulliken

notation• Varsányi notation

• Normal modes of molecule labelled with respect to normal modes of benzene

• Benzene has D6h symmetry; lowers to C2v upon substitution

• Normal modes arranged in symmetry blocks, then by decreasing energy

• Does not account for energetic re-ordering

• Loses information on motion of vibrations

• Subdivides substituents into two classes;‘heavy’ and ‘light’

• Unclear division between the two classes

Gardner-Wright Notation

• Takes fluorobenzene as a template molecule

• Applies Mulliken labelling scheme(ie. decreasing energy ordering within symmetry blocks)

• Treats the target molecule’s substituent as a point mass

J Chem Phys 135 114305 (2011)

Introduction - Existing schemes

M notation - Mass trends - G-W Notation

Experiments

- Previous studies - Fluorobenzene - Fluorobenzene-d5

Conclusions - Future work

Mass Trends Introduction - Existing schemes

M notation - Mass trends - G-W Notation

Experiments

- Previous studies - Fluorobenzene - Fluorobenzene-d5

Conclusions - Future work

J Chem Phys 135 114305 (2011)

Some mode switching seen for lower masses

Mass trends settle down quite quickly

Lowest mass atomic substituent would be fluorine

x = 1 - 20

Gardner-Wright Notation

• Takes fluorobenzene as a template molecule

• Applies Mulliken labelling scheme(ie. decreasing energy ordering within symmetry blocks)

• Treats the target molecule’s substituent as a point mass

J Chem Phys 135 114305 (2011)

Introduction - Existing schemes

M notation - Mass trends - G-W Notation

Experiments

- Previous studies - Fluorobenzene - Fluorobenzene-d5

Conclusions - Future work

• Uses Duschinsky mixing approach to show correlation between normal modes in different molecules

• Produces a Duschinsky matrix

Gardner-Wright Notation Introduction - Existing schemes

M notation - Mass trends - G-W Notation

Experiments

- Previous studies - Fluorobenzene - Fluorobenzene-d5

Conclusions - Future work

M18 and M19 mix heavily upon excitation

‘True’ Duschinsky Mixing

GeneralisedDuschinsky Mixing

Previous Studies• Lipp and Seliskar (1981)

J. Mol. Spec., 87, 242 (1981)

Vapour-phase absorptionFC6H5 and FC6D5

• Butler, Moss, Yin, Schmidt,and Kable (2007)J. Chem. Phys., 127, 094303 (2007)

Laser induced fluorescence and dispersed fluorescence

More than 40 DF spectra

• Pugliesi, Tonge, and Cockett (2008)J. Chem. Phys., 129, 104303 (2008)

RICC(2) frequency calculationsZEKE spectroscopy

Introduction - Existing schemes

M notation - Mass trends - G-W Notation

Experiments

- Previous studies - Fluorobenzene - Fluorobenzene-d5

Conclusions - Future work

Fluorobenzene-h5

Introduction - Existing schemes

M notation - Mass trends - G-W Notation

Experiments

- Previous studies - Fluorobenzene - Fluorobenzene-d5

Conclusions - Future work

(1 + 1) REMPI

Fluorobenzene-d5 and -h5

Introduction - Existing schemes

M notation - Mass trends - G-W Notation

Experiments

- Previous studies - Fluorobenzene - Fluorobenzene-d5

Conclusions - Future work

Fluorobenzene-h5

Fluorobenzene-d5

Fluorobenzene-d5

Introduction - Existing schemes

M notation - Mass trends - G-W Notation

Experiments

- Previous studies - Fluorobenzene - Fluorobenzene-d5

Conclusions - Future work

Observedposition /

cm-1

PotentialAssignme

nts

789.0

M8

M143M18

M16M18

M13M19

801.2M14M18M30

M192

809.8 M15M20

837.4

M14M20M29

M27

M13M17

M14M182M20

850.4M7

M17M19

M142M29

Observedposition /

cm-1

PotentialAssignme

nts

701.4702.6705.0

M16M20

M143M20

M17M18

708.8 M14M20M30

717.0718.2

M10

M14M16

M144

Observedposition /

cm-1

PotentialAssignments

917.0

M13M16

M18M20M29

M13M20M30

M13M143

928.0929.0929.6931.0933.6934.8

M142M19M20

M17M203

M19M20M30

M13M14M30

M14M18M29

M9

M12M17

M14M183

957.4M14M19M30

M13M18M202

Conclusions Introduction - Existing schemes

M notation - Mass trends - G-W Notation

Experiments

- Previous studies - Fluorobenzene - Fluorobenzene-d5

Conclusions - Future work

Future Work

• Record 2D-LIF spectra of fluorobenzene

• Possibility of time-resolved study

• Show usefulness of scheme when applied to other monosubstituted benzenes - coming up next!

Introduction - Existing schemes

M notation - Mass trends - G-W Notation

Experiments

- Previous studies - Fluorobenzene - Fluorobenzene-d5

Conclusions - Future Work

Acknowledgements

Prof. Timothy G. Wright

Anna Andrejeva

William Tuttle

Igor Pugliesi

Christian Schriever