Transcript Document
2D
Pump-probe spectroscopy: fast versus slow nuclear dynamics
H
(
r
,
R
)
p r
2 2
m r
p R
2 2
m R
U
(
r
,
R
)
m r
“Born Oppenheimer” approximation:
m R
(
r
,
R
,
t
)
n
(
r
,
R
) (
R
,
t
) H-O stretch motion (fast subsystem):
p r
2
m r
2
1D
U
(
r
,
R
)
n
(
r
,
R
)
E n
(
R
)
n
(
r
,
R
),
n
0 , 1 , 2 ...
Nuclear Hamiltonian of slow subsystem: ~
H n
p R
2 2
m R
E n
(
R
)
Pump-probe spectroscopy in the framework of BO
Water Dimer
Pump field
V L
d
01
E L
(
t
) cos(
L t
)
mixes two lowest OH vibrational states
(
t
)
0
(
r
,
R
)
0
(
R
,
t
)
1
(
r
,
R
)
1
(
R
,
t
)
0 1 ,
i
t
~
H
~
H
~
H V L
0 10
V L
~
H
1 01
Probe field:
prob
,
,
Dynamics of femtosecond O-O stretch motion
Property Toolbox
Dependence of collisional dephasing rate on photon detuning
ij
( )
ij
( 0 ) ( )
Homogeneous broadening Life-time broadening Collisional dephasing rate
ij
( 0 ) 1 2 (
i
j
),
ij
( ) ( 0 )
e
(
ij
) /
a
,
ij
| | ( 0 )
t scat
t col
ij
( )
ij
( 0 )
Kenji Kamada measurements
Example: PRL-101 Ab initio results:
AM1 geometry/6-31G*/DFT Quadratic Response
TPA
1280 GM at
0.1
eV
Non-linear pulse propagation
T (1 W/cm 2 ) = 0.994
L = 5 mm
= 140 fsec
= 0.1 eV
Non-linear pulse propagation
Non-linear pulse propagation
Exponential decay of red wing of linear absorption profile In case of Lorentzian decay TPA cross section is unrealistically high Inhomogeneous broadening of TPA spectra is not considered
Sensor Protection
Sensor Protection
Protection against lasers
Swedish Defence Nanotechnology Program 2004-11-17
Sensor Protection
The Project Group/Co-Workers
Preparation of materials
• • •
Dr. Bertil Eliasson, UmU, Sweden
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Marcus Carlsson, PhD student Dr. Eva Malmström, KTH, Sweden
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Robert Vestberg, PhD student Robert Westlund, PhD student Dr. Stephane Parola, UCBL, France
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Marcus Örtenblad, PhD student
• •
Modeling Prof. Hans Ågren, KTH, Sweden
– –
Oscar Rubio Pons, PhD student Peter Cronstrand, PhD student Dr. Patrick Norman, LiU, Sweden
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Johan Henriksson, PhD student Optical Equipment design
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Dr. Henrik Ludwigs, Saab Tech AB
• • •
Characterization Prof. Mikael Lindgren, NTNU, Norway
– –
Dr Jonas Örtegren, Post Doc Eirik Glimsdal, Dipl. Stud Dr. Anders Eriksson, FOI, Sweden Dr. Cesar Lopes, FOI, Sweden
Swedish Defence Nanotechnology Program 2004-11-17
Sensor Protection
Project Goals
Design and preparation of solid-state materials, with ability to clamp the transmitted energy ≤1
J @ 60% photopic transmission, for protection of eyes, E/O sensors and NVG against µs – ps pulses.
Preparation Characteriz.
Modeling
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Preparation
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Dendrimers
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Nanohybrid materials
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Solid-state glass materials
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Characterization
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Transmission
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OPL - Clamping
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Mechanisms
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Modeling
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The matrix - influence
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Concentration
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New nanomaterials
Swedish Defence Nanotechnology Program 2004-11-17
Sensor Protection
Solid-state optical limiting materials -Hybrid nanocomposites-
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Enhanced chemical, physical and mechanical long term stability
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Enhanced performance
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Environmentally friendly composition
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Shape processability Synthesis: Precursor Dendrimer ligand Synthesis: Precursor Me-organic compound Synthesis: Precursor Nanohybrid material Preparation Glass material Solid-state material Hybrid material Organic matrix
Swedish Defence Nanotechnology Program
Solid-state material Hybrid material Inorganic matrix
2004-11-17
Sensor Protection
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Preparation of solid materials
Dendrimers
– –
Coating Preparation of solids, organic matrix
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Glass materials
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Nanohybrid precursors Class I and II materials Alcohol (EtOH, MeOH) / H 2 2 O / Acid (HCl)
Si(OR) 4 4 Si(CH 3 )(OEt) 3 3
Aging, polymerization Sol Gel Drying
Swedish Defence Nanotechnology Program 2004-11-17
Sensor Protection
Class II nanohybrid materials
Stable upon hydrolysis NLO function
Si OR OR OR
+ Si(OR) 4 + H 2 O Hydrolysable groups
Class II solid state material
Swedish Defence Nanotechnology Program 2004-11-17
Sensor Protection
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Optical characterization
OPL characterization (standard f/5 set-up) Attenuation LASER
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Spectroscopy
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Optical absorption (UV-VIS and excited state absorption)
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Steady state and time-resolved luminescense spectroscopy Referens Detector OPL material Beam Splitter Beam expander
L1 L2 L3
Detector
Swedish Defence Nanotechnology Program 2004-11-17
Sensor Protection
Sample preparation
Precision saw machine (Isomet 1000) and polishing machine (Logitech PM2)
Swedish Defence Nanotechnology Program 2004-11-17
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Results year 1
Pt-Thiacalixarenes 50 mM och 12.5 mM
Swedish Defence Nanotechnology Program 2004-11-17
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Results year 1
Synthesis and characterization of new NLO chromophores Dendrimer capped Pt-aryl-ethynyls – preliminary OPL:
10 8 6 4 2 0 0 Pt1 50 PtG1 100 Input energy ( J) PtG2 PtG3 150 PtG4 Swedish Defence Nanotechnology Program 2004-11-17
Sensor Protection
Results year 1
Preparation of solid OPL materials : sol-gel
HO HO HO O HO O O HO O O O O HO HO O O HO HO HOHO O O O O HO O O O O O O O O O OH O O O O O O HO O O O OH O O OH OH O OH O OH O O O O O O O O O O O O O OH OH OH O O OH OH O OH O OH O O O O O O O O HO OH
Boltorn H30
O O P(Bu) 3 Pt P(Bu) 3
PtG2
O O O O O O O O O O Swedish Defence Nanotechnology Program 2004-11-17
Sensor Protection
Scientific output 2003 - 2004
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~ 25 publications
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P. Norman and H. Ågren ”First principles quantum modeling of optical power limiting” J. Comp. Theoretical Nanoscience, 2004 (in press)
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R. Vestberg, A. Nyström, M. Lindgren, E. Malmström and A. Hult ”Encapsulation of porphyrin cores by bis-MPA dendrons” Chemistry of Materials 16, (2004), 2794
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P. Cronstrand, P. Norman, Y. Luo and H. Ågren ”Few states models for three-photon absorption”
J. Chem. Phys. 121, (2004), 2020
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R. Vestberg, C. Nilsson, C. Lopes, B. Eliasson and E. Malmström ”Thiophene cored bis-MPA dendrimers for OPL applications”
Journal of Polymer Science Part A: Polymer Chemistry (2004)
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R. Vestberg, A. Eriksson, C. Lopes, M. Lindgren and E. Malmström ”Novel dendrimer-capped Pt-acetylides for OPL”
SPIE 5621, 2004
Swedish Defence Nanotechnology Program 2004-11-17
Porphyrin-cored 2,2-bis(methyole)propionic acid dendrimers 2,2-bis(methylol)propionic acid (bis MPA) dendrimers have been obtained by the direct addition of bis-MPA dendrons to free-base and Zn-porphyrins.
The growth of dendrimers in the case of Zn-TPP = tetrakis(4-hydroxyphenyl) porphine = is shown here.
Free-base TPP in G3 Fluorescence of dendrimers in THF No difference in emission for different generations of free base.
For Zn-cored porphyrins the shoulder at 650 nm increases with increasing generation.
Zn-TPP in Gx dendrimers
We have compared dendrimer spectra with FBP and ZnP emission spectra in different solvents and solid matrices and also with IR and Raman spectra (nonresonance and normalRaman). Comparative theoretical study of all these spectra, including simple models of dendrimers (Zn-TPP) at different levels (DFT and AM1)permits us the following explanations
This vibration is observed in Raman spectra at 1609 cm -1 and is identified with 1614 cm -1 vibronic 0-1 band in fluorescence ( n 10 of a g type).
It is seen as a shoulder at 720 nm for free-base-TPP fluorescence in G3 dendrimer. It is shifted in TPP to lower frequency.
The band is induced by large FC factor. No Herzberg-Teller contribution (a g )
In Zn-TPP molecule this mode is mixed with the phenyl stretchings. Phenyl rings are out-of porphpyrin-plane. When they bear bulky dendric MPA-substitutients this strongly influences electronic cloud of the Zn-porphpyrin chromophore The Herzberg-Teller mechanism now contributes more to intensity of vibronic line.
It influence mixing of the S 1 (Q x ) and the Soret states.
Vibronic shoulder at 660 nm in ZnTPP fluorescence; its intensity increases with dendrimer generation. It is induced by Herzberg-Teller effect In Zn-P molecule this band is changed in comparison with FBP, since it includes now Zn-N vibrations (asymmetric wagging movement). This is b 2g mode which includes also C a -C m vibrations in methyne bridges.
Among other low-frequency vibronic bands there is the nu 27 = 755cm -1 , which also includes the vibrations in methyne bridges and Zn movement.
The similar Herzberg-Teller mechanism contributes to intensity of this vibronic line with growing dendric MPA-substitutients.
It gives additional emission band (two-hump shoulder) in G5 fluorescence
This is ullustrated by Zn-TPP vibrations calculated at AM1 level
Phosphorescence of free-base porphin and Zn-porphyrin.
The efficient inter-system crossing of porphyrins, which maintain a high concentration of triplet-excited molecules is used now in a wide variety of applications from photodynamic therapy to nonlinear optical devices. We have explained for the first time the low phosphorescence efficiency of porphyrins without heavy ions by DT DFT calculations.
We have obtained a slow radiative rate constant of the lowest triplet state, 3 B 2u , of free-base porphin phosphorescence (about 10 -3 s -1 ), which is in agreement with experimental estimations.
Phosphorescence of free-base porphin is determined by emission from the most active T z spin sublevel, where z-axis coinsides with the N-H...H-N bond direction. It is polarised perpendicular to the molecular plane.
Such a slow radiative decay is very unusual for a molecule wich possesses lone pairs of electrons at nitrogen atoms and a number of excited n p * states in the near UV region. It is explained by destructive interference of S-S and T-T contribution.