Vladimir Roudnev and B.D. Esry
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Transcript of Vladimir Roudnev and B.D. Esry
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HD+ Photodissociation in an Ultrashort Infrared Laser
Pulse: Carrier-Envelope Phase Difference Effects
Vladimir Roudnev and
B.D. Esry
The work is supported by the Chemical Sciences, Geosciences and Biosciences Division, Office of Basic Energy Sciences, Office of Science, Us. Department of
Energy, and by the Research Corp.
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Motivation
Could any asymmetry be observed in HD+
photodissociation?
How to treat dissociation processes in the presence of ionization?
What kind of asymmetries might be expected?
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Topics3D model (1 nuclear+2 electron degrees of freedom) of the HD+
ion in a laser fieldNumerical solution of the time-dependent Schroedinger equation
(TDSE)The HD+ ion in the field of intense (4× to 9×1014W/cm2) 10fs
linearly polarized 790 nm laser pulse: calculation resultsCarrier-envelope phase effects observability for reaction
probabilitiesFragments' velocity distribution in scaled coordinate approach
Carrier-envelope phase effects observability for fragments' velocity distributions
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Coordinate system for HD+ molecule
xeye
E
Intrinsic coordinates:
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Time-dependent Schroedinger equation
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The time evolution
• Operator splitting
● Cayley approximant
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Single and double-scale approximants
Partial approximants
Double-scale approximant
Single-scale approximant
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Ionization probabilities intensity dependence
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Channel separation: domains in the configuration space
Different channels can be identified by the corresponding domains in the configuration space
z
R
H+d
p+D
M
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Electron density distribution
z (a.u.)
t (a.u.)
I=8 1014 W/cm2
CEPD=π
H+d channel dominates
I=8 1014 W/cm2
CEPD=0
D+p channel dominatesz (a.u.)
t (a.u.)
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Dissociation probabilities phase dependence
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Laser phase averaged dissociation probabilities
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Orientation averaged dissociation probabilities
I=6×1014 W/cm2 I=7×1014 W/cm2
I=8×1014 W/cm2 I=9×1014 W/cm2
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The dissociation asymmetry observability
●Controlled carrier-envelope phase difference●Oriented molecules
●Controlled carrier-envelope phase difference●Not oriented molecules
●Uncontrolled carrier-envelope phase difference
Channel asymmetry is revealed in total dissociation
Channel asymmetry is revealed in spatial distribution of dissociated fragments
No channel asymmetry is expected
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Scaled coordinates approach
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Scaled coordinate approach: properties
– Bound states shrink with time– Continuum states approach a stationary distribution at large times– Momentum distribution of the continuum part can be obtained
from the asymptotic stationary state by simple rescaling– Continuum states converge to the rescaled momentum distribution
faster than O(R(t)-3/2)
Rescaling:
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Scaled coordinates distribution converges to momentum distribution
Free particle Bound state in a laser field
t=2500
t=1500
t=3500
t=0
t=5
t=10
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Fragment velocity distribution CEPD variation
D velocity (au)H velocity (au)
CEP
D/π
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Orientation averaged fragment velocity distribution
CEPD variation
D velocity (au)H velocity (au)
CEP
D/π
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CEPD effects for the fragments of fixed velocity
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Summary• Strong CEPD effects are expected for
dissociation of the HD+ molecule in 10 fs 785 nm laser pulse
• Reaction asymmetries can be observed only if the laser CEPD is controlled, charged and neutral reaction fragments must be registered separately
• The effect is much stronger if fragment velocity selection is performed
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Future• What are the velocity distributions for
ionization? • How the initial state affects the results?
• How to improve the accuracy/perfomance?