DYNAMICS AROUND CRITICAL FEATURES OF ENERGY LANDSCAPES BRUXELLES N. Vaeck ORSAY D. Lauvergnat Y. Justum B. Lasorne M. Desouter-Lecomte LYON M.-C. Bacchus K. Piechowska LIEGE G. Dive

I. RESEARCH AREA OF THE TEAM II. METHODOLOGY III. CRITICAL REGIONS OF ENERGY LANDSCAPES IV. OBJECTIVES IN THE RADAM NETWORK I. RESEARCH AREA OF THE TEAM II. METHODOLOGY III. CRITICAL REGIONS OF ENERGY LANDSCAPES IV. OBJECTIVES IN THE RADAM NETWORK

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 Particular regions leading to quantum effects Dynamics involving few active degrees of freedom Ultrafast processes t < 1 ps Ultra fast local quantum dynamics

Molecular system H Segregation between active (q) and inactive (Q) coordinates q : at least the n principal coordinates involved in the reaction path II. METHODOLOGY Rigid or flexible constraints Constrained subsystem H constrained + Dissipation

II. METHODOLOGY  Select n active coordinates q H constrained nD = V nD (q) ab initio = V nD (q) ab initio + T nD + T nD  Compute a PES V nD (q)  Choose rigid or flexible kinematical model Q eq (q) = Q c or ∂Q eq (q)/∂q ≠ 0  Construct the corresponding constrained KEO T nD

II. METHODOLOGY T NUM 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, Constrained Hamiltonians

III. CRITICAL FEATURES OF ENERGY LANDSCAPES Rate constant Tunneling A. Regions of strong non adiabatic interaction B. Bifurcating regions C. Transition states IVR between reaction coordinate and deformation Electron transfer Ultra fast internal conversion Conversion of an optical signal into mechanical motion Non B-OB-O

A. Regions of strong non adiabatic interaction Conical intersection M.-C. Bacchus K. Piechowska CASSCF/cc-pvtz Avoided crossing d CO d CBr or d CCl M.-C. Bacchus N. Vaeck CASSCF/cc-pvdz V 2D Up funnel Ultra Fast decay

Diabatic trapping or up-funnel process Paradoxical decrease of product yield at increasing excitation energy Photoisomerization of the Yellow proteine chromophore (p-trans coumaric acid) in S 1 state up-funnel S 1 /S 2 and turn around towards another channel C. Ko et al. JACS 125, (2003) Avoided crossing R E R E

= 248 nm Competitive dissociation of bromoacetyl chloride Experimental branching ratio Cl:Br = 1.0:0.4 Diabatic trapping A’’ A’ C C H H O Cl Br

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) Diabatic trapping

Active coordinates Two 2D subspaces Spectator modes Two deformations frozen at the Franck-Condon geometry Other modes optimized in the first A" excited state CO Barrier Seam Dynamics of photodissociation CBr CCl M.-C. Bacchus N. Vaeck CASSCF/cc-pvdz

―: t = 0 ―: 12 fs ―: 24 fs ―: 36 fs ―: 48 fs --: 84 fs --: 96 fs Dynamics of photodissociation CO CBr Ratio of the dissociative fluxes in the CO/CBr and CO/CCl sides Experimental branching ratio Cl:Br = 1.0:0.4 F-C

Dynamics in excited states Works in prospect in collaboration with QCEXVAL University of Valencia, Spain M. Merchán y L. Serrano-Andrés, J. Am. Chem. Soc. 125, 8108 (2003) Cytosine Adenine/(H 2 O) n H. Kang, K.T. Lee, S.K. Kim, Chem. Phys. Letters 359, 213 (2002). Pump probe experience on adenine/(H 2 0) n

Bifurcation of valleys C O H  H H  B. Bifurcating regions : Valley Ridge Inflection Point Bifurcation of ridges   V 2D G. Dive QCISD 6-31G* G. Dive B3LYP 6-31G*

Bifurcating regions Dynamics of a wave packet around a VRI region   V 2D spreadin g 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 Competition between B. Lasorne, G. Dive, D. Lauvergnat and M. Desouter-Lecomte, J. Chem. Phys. 118, 5831 (2003)

TS 2 :TS 1 : P P P’ TS 1 TS 2 VRI Bifurcating regions Dimerisation of cyclopentadiene P. Caramella, P. Quadrelli & L. Toma, JACS 124, 1130 (2002)

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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 ?

Target Wave packet Target Initial Wave packet After 500 fs z z x x y y

H transfer C. Regions around transition states Reaction coordinate s   V tunnelin g Rate constant including tunneling by TSWP method using the flux operator eigenvectors B. Lasorne, F. Gatti, E. Baloïtcha, H.D. Meyer and M. Desouter- Lecomte, J. Chem.Phys In press

H exchange between hydroxyl radical and adenine. Complex absorbing potential s = s # constrained reaction path Hamiltonian G. Dive B3LYP/6-31G** Active coordinate : reaction coordinate s tunneling

Hydroxyl radical on nucleobases and ribose. reaction coordinate E ev C1C1 Works in prospect Rate constants

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 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

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 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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