Table Of Content" DTIC
AD-A252 653
JUL 3 19921
192
AD-A22 653
FOR PUBLIC DISTRIBUTION JUL
ONR Grant N00014-90-J-1014: Final Scientific Report
Title: Coherent Radiative Control of Chemical Reactions
Principal Investigator: P. Brumer, Professor, Chemical Physics Theory Group, De-
partment of Chemistry, University of Toronto, Toronto, Canada M5S lAl
(416-978-3569);
Subcontractor: M. Shapiro, Professor, Weizmann Institute of Science
ONR Scientific Officer: Dr. P. Reynolds
Grant Period: October 1989 - September 1992
Submitted by:
P. Brumer, Professor, Chemical Physics Theory Group, Dept. of Chemistry
M. Shapiro, Professor, Chemical Physics Department
92-17533
92 7 06 054
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?I..'" filB,
Grant-Supported Publications f.v_
The following papers describe research supported under this grant. Papers numbered .. ...
1-12, as well as a sample conference proceedings review (number 18) are included with ,
this report. 'VWal , i1
Publications:
A. Refereed Publications:
1. "Coherent Radiative Control of IBr Photodissociation via Simultaneous (W,W ) Ex-
1 3
citation", C.K. Chan, P. Brumer and M. Shapiro, J. Chem. Phys. 94, 2688 (1991).
2. "Interference Between Optical Transitions and Control of Relative Cross Sections",
C.K. Chan, P. Brumer and M. Shapiro, Phys. Rev Lett. 62, 3199 (1990).
3. "Two-Pulse Coherent Control of Electronic States in the Photodissociation of IBr:
Theory and Proposed Experiment", I. Levy, M. Shapiro and P. Brumer, J. Chem.
Phys. 93, 2493 (1990).
4. "Quantum Beats Induced by Partially Coherent Laser Sources", X-P. Jiang and P.
Brumer, Chem. Phys. Letters 180, 222 (1991).
5. "Controlled Photon Induced Symmetry Breaking: Chiral Molecular Products From
Achiral Precursors", M. Shapiro and P. Brumer, J. Chem. Phys. 95, 8658 (1991).
6. "Laser Induced Unimolecular Isomerization: Theory and Model Applications", D.
Gruner, P. Brumer and M. Shapiro, J. Phys. Chem. 96, 281 (1992).
2
7. "Laser Control of Molecular Processes", P. Brumer and M. Shapiro, Annual Reviews
of Physical Chemistry, 43, xxx, (1992) (in press).
8. "Theory of Resonant Two-Photon Dissociation of Na ", Z. Chen, M. Shapiro and P.
2
Brumer, J. Chem. Phys. (submitted).
9. "Coherent Radiative Control of Molecular Photodissociation via Resonant 2-Photon
vs. 2-Photon Interference", Z. Chen, P. Brumer and M. Shapiro, Phys. Rev. Lett.
(submitted).
10. "Three-Dimensional Quantum-Mechanical Computations of the Control of the
H+OD4-DOH-D+OH Reaction", M. Shapiro and P. Brumer, J. Chem. Phys.
(submitted).
11. "Multiproduct Coherent Control of Na Photodissociation via 2-Photon vs. 2-
2
Photon Interference", Z. Chen and P. Brumer and M. Shapiro, J. Chem. Phys.
(to be submitted).
12. "Total N-Channel Control in the Weak Field Domain", M. Shapiro and P. Brumer,
J. Chem. Phys. (submitted)
B. Manuscripts in Preparation:
13. "Partially Coherent Laser Pulses in Coherent Control of Chemical Reaction", X.P.
Jiang, M. Shapiro and P. Brumer.
14. "Initial Value Representation for Polyatomic Photofragmentation", G. Campolieti,
M. Shapiro and P. Brumer.
3
15. "SEP Preparation in Na Photodissociation and Control", J. Dods, P. Brumer and
2
M. Shapiro.
16. - Asymmetric Synthesis via Coherent Radiative Control of Molecular Photodissoci-
ation", M. Shapiro and P. Brumer.
17. "Control of Photochemistry", P. Brumer and M. Shapiro, to appear in "Molecules
in Laser Fields", ed. A. Bandrauk, (Marcel Dekker, N.Y.).
C. Conference Proceedings
18. "Coherence in the Control of Molecular Processes", P. Brumer and M. Shapiro, in
"Coherence Phenomena in Atoms and Molecules in Laser Fields", ed. A.D. Bandrauk
(in press).
19. "Quantum Interference and the Control of Molecular Processes", P. Brumer and M.
Shapiro, in "Mode Selective Chemistry", pgs. 323-331, ed. J. Jortner et al, (Kluwer,
Netherlands, 1991).
20. "Coherent Effects in Laser Chemistry", M . Shapiro and P. Brumer, in "Optical
Methods for Time and State Resolved Chemistry", ed. C. Ng, SPIE Proceedings,
Jan. 1992 (in press).
D. Publicationsp reviously reported (FinalR eport - 1989) as submitted, now published
21. "Coherent Radiative Control of Unimolecular Reactions: Selective Bond Breaking
with Picosecond Pulses", T. Seideman, M. Shapiro and P. Brumer, J. Chem. Phys.
90, 7132 (1989).
4
22. "Coherent Radiative Control of Bimolecular Reactions", J. Krause, M. Shapiro and
P. Brumer, J.C hem. Phys. 92, 1126 (1990).
23. "Coherence Chemistry: Controlling Chemical Reactions With Lasers", P. Brumer
and M. Shapiro, Accounts Chem. Res. 22, 407 (1989).
24. "Mode Selective Control of Reactions by Rapid or Shaped Laser Pulses: An Emperor
Without Clothes ", P. Brumer and M. Shapiro, Chemical Physics, 139, 221 (1989).
25. "Creation and Dynamics of Molecular States Prepared with Coherent and Partially
Coherent Pulsed Light", X-P. Jiang and P. Brumer, J.C hem. Phys. 94, 5833 (1991).
Work In Progress
26. "Coherent Radiative Control of Photodissociation on Surfaces", (with X-P. Jiang).
27. "Coherent Control in High Fields", (with Z. Chen).
28. " Natural Modes in HOD, HOT, etc.", (with X-P. Jiang).
29. "Semiclassical Propagation of Polyatomic Photofragmentation", (with J. Campoli-
eti).
30. "Quantum Calculations of Above Threshold Ionization", (with R. Blank).
31. "Quantum Computations of Polyatomic Photofragmentation", (with A. Abrashke-
vitch).
5
Research Accomplishments
We continue research on our method of coherent radiative control of chemical reactions,
extending the general theory and theoretically designing laboratory scenarios for displaying
control. We have, during the course of this grant period, done several seminal pieces of
research which both extend the theory and provide the basis for considerably greater
advances in the near future. Particularly notable successes during this research period
include:
a) the successful demonstration of extensive control in IBr photodissociation using both
a three photon + one photon scenario1'2 as well as a pump-dump scenario3;
b) the development of a theory of the interaction of molecules with a partially coherent
laser source4 and examination of the extent of control under these conditions13;
c) controlled asymmetric synthesis: the demonstration that coherent control can be
used to obtain chiral molecular products from achiral initial precursors' 16;
d) the development of a cw laser scheme which allows for controlled cis-trans isomerization6;
e) the first successful computation of control in a chemical reaction (here H+OD-DOH-
D+OH) which forms two chemically distinct product arrangments°;
f) the development of a resonant 2-photon plus 2-photon scheme which allows for the
control of chemical reactions in a thermal environment and eliminates other uncon-
trolled contributions' 9. Successful demonstration of control over two and three1
product channels in the dissociation of Na ;
2
6
g) the development of a semiclassical method for computing photodissociation in mul-
tiparticle systems14 and successful tests on a simple photodissociation model; and
h) the determination of conditions under which total control can be achieved in the
N-level problem 12 under weak field conditions.
In addition, work has begun on a number of new coherent control problems which serve
as the basis for our proposal for continued funding.
This report provides a very brief sketch of results obtained; the accompanying preprints
and reprints should be consulted for further details. We also note, later below, the appear-
ance of several experiments which have verified the essential principle of coherent control
in the one product channel case. Further experimental work, motivated by theoretical
developments, are in progress at various institutions.
A. Simultaneous w ,3w Excitation:
3 1
We have previously shown that photodissociation of single bound state by excitation
with frequencies w3 and 3w,, where 3hw, = hlw3, affords a method of doing control [M.
Shapiro, J.W. Hepburn and P. Brumer, Chem. Phys. Lett. 149, 451 (1988)]. Theoreti-
cally, control arises through the quantum interference induced between two optical routes
controlled by different transition operators, i.e. the one photon P and three photon T
operators. Here T is defined as
T = ( • /'1)e ,9 (Ei - Hg + 2hw)- ' (el • p)ge (E - He + hw)- ' (tl •)e.g
where Hg, H. are the ground and excited state Hamiltonians, el is the unit vector in the
direction of the electric field and E is the energy of the initial bound state Oi ). In this
7
instance the probability P(E, q) of observing a product at energy E and in arrangement
channel q is given by:
P(E,q) = (7)2 [3 n I( I'))+j2 E',n ('-ITI~i)I 2
2E3E'cos( 0 - 301 + )13 IFI- I
3
with the amplitude F( ) and phase b(') defined by:
1 je i.3? = J'(E,n,q)-) (Ob(E, n,q)- 1(3 / ),.gl i)
The first and second terms in P(E,q) give one photon and three photon dissociation
probabiities with fields of intensities s3 and El whereas the third term arises from the
quantum interference between these two processes. The latter term affords experimental
control over P(E, q). Specifically, by experimentally manipulating the laser electric field
amplitudes EI, E3 and relative phase of the lasers 03 - 301, one directly alters P(E, q).
To ascertain the extent of possible control in realistic systems we computationally
examined1' 2 coherent radiative control in the photodissociation of IBr, which produces I
+ Br and I + Br*, using high quality potential surfaces and fully quantum mechanical
photodissociation methods. Results showed that an extremely wide range of control (25%
to 95%) could be achieved by varying the relative laser phase and intensity over a modest
range. Such control was also maintained for high J states (J = 42), despite the required
extensive averaging over 85 Mj states. In this regard, also of interest, was the observa-
tion that the dependence on control parameters (relative laser phase and amplitude) is
relatively independent of the J values.
The fundamental principle of coherent control, as manifest in this 1 + 3 photon sce-
nario, has now been demonstrated experimentally [C. Chen, Y-Y. Yin, and D.S. Elliott,
8
Phys. Rev. Lett.,64, 507 (1990); S.M. Park, S-P. Lu, and R.J. Gordon, J. Chem. Phys. 94,
8622 (1991); B.A. Baranova, A.M. Chudinov and B. Ya Zel'dovitch, Opt. Comm., 79,
116 (1990)]. Extensions to include more than one product channel are being planned by
a number of experimental groups.
B. Pump-Dump Control in IBr Photodissociation:
Whereas the 1+3 photon scenario described above relies upon the interference at a
fixed energy induced by two different CW fields, an alternative approach [M. Shapiro
and P. Brumer, J. Chem. Phys. 90, 7132 (1989)] utilizes a pulsed laser to prepare a
superposition of two or more bound states and a subsequent dump laser to carry the system
to dissociation. Interference is induced in this scenario by the multitude of frequencies
within the second pulse which carry each member of the superposition to the same range
of continuum energies E.
In the general case the initial excitation pulse T,(t), creates a linear superposition state
in the excited state and the temporally separated dump pulse Td(t) brings the system to
the regime wherc products are energetically accessible. The state prepared after the ?' (t)
is given in first order perturbation theory by:
I = leEg( t))e)- iE tlh + cjl E,)eEjt/h
with
cj= (\/'27/ih)( Ej pl Eg)Ex( wjg) = d3E.(w39)
where wjg = (Ej - Eg)/h, the excitation frequency to level I Ej ) from the ground state
I Eg ) and where d. is defined by the second equality. Note that E,(w) or Cd(W) denote the
Fourier transform of the respective laser pulse.
9
