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Pump-probe spectroscopy: fast versus slow nuclear dynamics
),(),(),,( tRRrtRr n
“Born Oppenheimer” approximation:
Rr mm
),(22
),(22
RrUm
p
m
pRrH
R
R
r
r
H-O stretch motion (fast subsystem):
...2,1,0),,()(),(),(2
2
nRrRERrRrU
m
pnnn
r
r
Nuclear Hamiltonian of slow subsystem:
)(2
~ 2
REm
pH n
R
Rn
2D
1D
Ht
i~
110
010
1
0~
~~
,HV
VHH
L
L
Pump-probe spectroscopy in the framework of BO
),(),(),(),()( 1100 tRRrtRRrt
Pump field )cos()(01 ttEdV LLL
Water Dimer
mixes two lowest OH vibrational states
Probe field: ,, prob Dynamics of femtosecond O-O stretch motion
linearnonlinear
Property Toolbox
magnetic
electr
icinternal
external
time-dep
Time-indep
a = 13 nm
Dependence of collisional dephasing rate on photon detuning
Homogeneousbroadening
Life-timebroadening
Collisionaldephasing
rate
a = 80 nm
Kenji Kamada measurementsKenji Kamada measurements
Example: PRL-101
AM1 geometry/6-31G*/DFT Quadratic ResponseAM1 geometry/6-31G*/DFT Quadratic Response
TPA 1280 GM at 1280 GM at eVeV
Ab initio results:Ab initio results:
Non-linear pulse propagation
L = 5 mmL = 5 mm
= 0.1 eV= 0.1 eV
T (1 W/cmT (1 W/cm22) = 0.994) = 0.994
= 140 fsec= 140 fsec
Non-linear pulse propagation
Non-linear pulse propagation
Exponential decay of red wingExponential decay of red wingof linear absorption profileof linear absorption profile
In case of Lorentzian decay TPAIn case of Lorentzian decay TPAcross section is unrealistically highcross section is unrealistically high
Inhomogeneous broadening of Inhomogeneous broadening of TPA spectra is not consideredTPA spectra is not considered
Swedish Defence Nanotechnology Program 2004-11-17
Sensor Protection
Sensor ProtectionProtection against lasers
Swedish Defence Nanotechnology Program 2004-11-17
Sensor Protection
The Project Group/Co-Workers
• Dr. Bertil Eliasson, UmU, Sweden
– Marcus Carlsson, PhD student
• Dr. Eva Malmström, KTH, Sweden
– Robert Vestberg, PhD student
– Robert Westlund, PhD student
• Dr. Stephane Parola, UCBL, France
– Marcus Örtenblad, PhD student
Preparation of materials• Prof. Hans Ågren, KTH, Sweden
– Oscar Rubio Pons, PhD student
– Peter Cronstrand, PhD student
• Dr. Patrick Norman, LiU, Sweden
– Johan Henriksson, PhD student
Modeling
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
Optical Equipment design• Dr. Henrik Ludwigs, Saab Tech AB
Swedish Defence Nanotechnology Program 2004-11-17
Sensor Protection
Project GoalsDesign 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.
ModelingCharacteriz.
Preparation
• Preparation
• Dendrimers
• Nanohybrid materials
• Solid-state glass materials
• Characterization
• Transmission
• OPL - Clamping
• Mechanisms
• Modeling
• The matrix - influence
• Concentration
• New nanomaterials
Swedish Defence Nanotechnology Program 2004-11-17
Sensor Protection
• Enhanced chemical, physical and mechanical long term stability
• Enhanced performance
• Environmentally friendly composition
• 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
Solid-state material Hybrid material Inorganic matrix
Solid-state optical limiting materials -Hybrid nanocomposites-
Swedish Defence Nanotechnology Program 2004-11-17
Sensor Protection
Preparation of solid materials• Dendrimers
– Coating– Preparation of solids,
organic matrixAlcohol (EtOH, MeOH) / H2O / Acid (HCl)Alcohol (EtOH, MeOH) / H2O / Acid (HCl)
Si(OR)4 [R = Et, Me],Si(CH3)(OEt)3
Si(OR)4 [R = Et, Me],Si(CH3)(OEt)3
PrecursorsPrecursors
Sol
Gel
Drying
Doped monolithDoped monolith
Aging, polymerization
• Glass materials– Nanohybrid precursors– Class I and II materials
Swedish Defence Nanotechnology Program 2004-11-17
Sensor Protection
SiNLO function
OROROR
Stable upon hydrolysis
Hydrolysablegroups
Class II nanohybrid materialsClass II nanohybrid materials
+ Si(OR)4
+ H2O Class II solid-state material
Swedish Defence Nanotechnology Program 2004-11-17
Sensor Protection
Optical characterization• OPL characterization
(standard f/5 set-up)
LASER
ReferensDetector
Beam Splitter L1 L2 L3 DetectorBeam
expander
OPL-material
Attenuation
• Spectroscopy– Optical absorption (UV-VIS and
excited state absorption)– Steady state and time-resolved
luminescense spectroscopy
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
Sensor Protection
Results year 1
Pt-Thiacalixarenes50 mM och 12.5 mM
Swedish Defence Nanotechnology Program 2004-11-17
Sensor Protection
Results year 1Synthesis and characterization of new NLO chromophoresDendrimer capped Pt-aryl-ethynyls – preliminary OPL:
0
2
4
6
8
10
0 50 100 150Input energy ( J )
Out
put e
nerg
y (
J)
Pt1 PtG1 PtG2 PtG3 PtG4
Swedish Defence Nanotechnology Program 2004-11-17
Sensor Protection
Results year 1
Preparation of solid OPL materials : sol-gel
O
O
O O
O
O
O
O
O O
O
O
O O
OH
OH
O
OOH
OH
O
OH
O
O
OH
OH
O
O
O
O
O
O
HOHO
O
O
HO
HO
O
HO
OO
OHHO
O
O
OO
O
O
HO
HO
O
O
HO
HO
O
HO
O
O
HO
HO
O
O
O
O
O
O
OHOH
O
O
OH
OHO
OH
O
OHO
OH
Boltorn H30
PtP(Bu)3
P(Bu)3 OO
OOO
O
O O
OO
O
O
O
O
OO
OO
O
O
PtG2
Swedish Defence Nanotechnology Program 2004-11-17
Sensor Protection
Scientific output2003 - 2004
• ~ 25 publications• P. Norman and H. Ågren
”First principles quantum modeling of optical power limiting”J. Comp. Theoretical Nanoscience, 2004 (in press)
• 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
• P. Cronstrand, P. Norman, Y. Luo and H. Ågren”Few states models for three-photon absorption”J. Chem. Phys. 121, (2004), 2020
• 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)
• R. Vestberg, A. Eriksson, C. Lopes, M. Lindgren and E. Malmström”Novel dendrimer-capped Pt-acetylides for OPL”SPIE 5621, 2004
Porphyrin-cored2,2-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 Zn-TPP in Gx dendrimers
Fluorescence ofdendrimers 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.
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 (10 of ag 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 (ag)
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 b2g mode which includes also C-Cm vibrations in methyne bridges.
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 S1(Qx) and the Soret states.
Among other low-frequency vibronic bands there is the nu27 = 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, 3B2u, 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 Tz 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* states in the near UV region. It is explained by destructive interference of S-S and T-T contribution.
