Diapositive 1

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DYNAMICS AROUND CRITICAL FEATURES OF ENERGY
LANDSCAPES
BRUXELLES N. Vaeck
LIEGE G. Dive
ORSAY D. Lauvergnat Y.
Justum B. Lasorne M.
Desouter-Lecomte
LYON M.-C. Bacchus K.
Piechowska
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I. RESEARCH AREA OF THE TEAM II.
METHODOLOGY III. CRITICAL REGIONS OF ENERGY
LANDSCAPES IV. OBJECTIVES IN THE RADAM NETWORK
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I. RESEARCH AREA
Quantum description of elementary processes in
gas phase 1) Electrons ab initio quantum
chemistry calculations of PES 2) Nuclei wave
packet dynamics
Chemical reactivity exploration of an
energy landscape by a wave packet possibly guided
by a laser field
Dynamics involving few active degrees of freedom
Ultrafast processes t lt 1 ps
Particular regions leading to quantum effects
Ultra fast local quantum dynamics
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II. METHODOLOGY
Molecular system H
Segregation between active (q) and inactive (Q)
coordinates q at least the n principal
coordinates involved in the reaction path
Rigid or flexible constraints
Constrained subsystem Hconstrained
Dissipation
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II. METHODOLOGY
VnD(q) ab initio
TnD
Hconstrained nD

• Select n active coordinates q

• Compute a PES VnD(q)

• Choose rigid or flexible kinematical model
• Qeq(q) Qc or ?Qeq(q)/?q ? 0

• Construct the corresponding constrained KEO
• TnD

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II. METHODOLOGY
Constrained Hamiltonians
TNUM generates numerically but exactly the values
of the coefficients of the differential operators
at any grid point. D. Lauvergnat A. Nauts, J.
Chem. Phys. 116, 8560 (2002)
D. J. Rush et K. B. Wiberg, J. Phys. Chem. A
101, 3143 (1997), J. R. Durig et W. Zhao, J.
Phys. Chem. 98, 9202 (1994) S. Sakurai N.
Meinander et J. Laane, J. Chem. Phys. 108, 3537
(1998) M. L. Senent, CPL 296, 299 (1998), D.
Luckhaus, J. Chem. Phys. 113, 1329 2000
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III. CRITICAL FEATURES OF ENERGY LANDSCAPES
Non B-O
B-O
B. Bifurcating regions
A. Regions of strong non adiabatic interaction
IVR between reaction coordinate and deformation
Electron transfer Ultra fast internal
conversion Conversion of an optical signal into
mechanical motion
C. Transition states
Rate constant Tunneling
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A. Regions of strong non adiabatic interaction
Conical intersection
Avoided crossing
dCO
dCBr or dCCl
M.-C. Bacchus K. Piechowska CASSCF/cc-pvtz
M.-C. Bacchus N. Vaeck CASSCF/cc-pvdz
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Diabatic trapping or up-funnel process
Avoided crossing
Paradoxical decrease of product yield at
increasing excitation energy
E
Photoisomerization of the Yellow proteine
chromophore (p-trans coumaric acid) in S1
state up-funnel S1/S2 and turn around towards
another channel C. Ko et al. JACS 125, 12710
(2003)
R
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Diabatic trapping
Competitive dissociation of bromoacetyl chloride
Cl
A
Br
A
l 248 nm
Experimental branching ratio ClBr 1.00.4
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Diabatic trapping
M.D. Person, P.W. Kash L.J. Butler, J. Chem.
Phys. 97, 355 (1992) CISD/STO-3G W.-J. Ding et
al, Journal Chemical Physics 117, 8745 (2002)
CAS(8,7)/6-31G MRCI B. Lasorne, et al, J.
Chem. Phys. 120, 1271, 2004 CASSCF/cc-pvdz (18)
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Dynamics of photodissociation
CO
Active coordinates Two 2D subspaces Spectator
modes Two deformations frozen at the
Franck-Condon geometry Other modes optimized in
the first A" excited state
Seam
Barrier
CBr
CO
M.-C. Bacchus N. Vaeck CASSCF/cc-pvdz
Seam
Barrier
CCl
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Dynamics of photodissociation
Ratio of the dissociative fluxes in the CO/CBr
and CO/CCl sides
? t 0 ? 12 fs ? 24 fs ? 36 fs ? 48
fs -- 84 fs -- 96 fs
CO CBr
F-C
Experimental branching ratio ClBr 1.00.4
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Dynamics in excited states
Works in prospect
Cytosine
M. Merchán y L. Serrano-Andrés, J. Am. Chem. Soc.
125, 8108 (2003)
in collaboration with QCEXVAL University of
Valencia, Spain
H. Kang, K.T. Lee , S.K. Kim, Chem. Phys. Letters
359, 213 (2002).
Adenine/(H2O)n
Pump probe experience on adenine/(H20)n
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B. Bifurcating regions Valley Ridge Inflection
Point
Bifurcation of valleys
Bifurcation of ridges
G. Dive QCISD 6-31G
G. Dive B3LYP 6-31G
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Bifurcating regions
Dynamics of a wave packet around a VRI region
Competition between
Time of spreading in a flat region Width when
entering the VRI region Curvature of the ridge
Time of flight along the ridge Lenght of the
ridge Gradient along the ridge Kinetic energy
spreading
B. Lasorne, G. Dive, D. Lauvergnat and M.
Desouter-Lecomte, J. Chem. Phys. 118, 5831
(2003)
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Bifurcating regions
P
Dimerisation of cyclopentadiene
TS1
TS2
VRI
P
P
TS1
TS2
VRI
P
P. Caramella, P. Quadrelli L. Toma, JACS 124,
1130 (2002)
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0 fs
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10 fs
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20 fs
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30 fs
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40 fs
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50 fs
24
60 fs
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70 fs
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0 fs
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10 fs
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20 fs
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30 fs
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40 fs
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50 fs
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60 fs
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70 fs
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Bifurcating regions
Offers a rich variety of behaviours according to
the shape of the wave packet
Key regions for branching ratios in the
unsymmetrical case
Key regions in the control by laser field ?
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Key regions in the control by laser field ?
InitialWave packet
Target
TargetWave packet
After 500 fs
Target
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C. Regions around transition states
Rate constant including tunneling
H transfer
tunneling
V
by TSWP method using the flux operator
eigenvectors
Reaction coordinate s
0
p
B. Lasorne, F. Gatti, E. Baloïtcha, H.D. Meyer
and M. Desouter-Lecomte, J. Chem.Phys. 2004 In
press
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H exchange between hydroxyl radical and adenine.
constrained reaction path Hamiltonian
s s
Active coordinate reaction coordinate s
G. Dive B3LYP/6-31G
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Works in prospect
Rate constants
Hydroxyl radical on nucleobases and ribose.
C1
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OUR OBJECTIVES IN THE RADAM NETWORK
Preliminary step collect data at microscopic
level

• Target
• understand the mechanisms of elementary
  processes involving quantum effects after
  irradiation of biomolecules
• compute and hopefully control branching ratio
  and rate of
• photodissociation
• photoisomerization
• electron, proton and H transfer

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Tools Quantum dynamics in reduced
dimensionality in fundamental and excited
states including a laser field dissipative
effects around conical intersections, avoided
crossings and bifurcating regions
Further step macroscopic level
Inclusion of these data in kinetic schemes for
cellular processes reaction chains or
selforganization
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Thank you for your attention