Phase Transitions in the Picosecond Time Domain

1986 ◽  
Vol 77 ◽  
Author(s):  
Hani E. Elsayed-Ali ◽  
Gerard A. Mourou
Keyword(s):  
Laser Heating ◽  
Lattice Relaxation ◽  
Nonequilibrium State ◽  
Metal Films ◽  
Ultrafast Laser ◽  
Femtosecond Laser Irradiation ◽  
Lattice Temperature ◽  
Physical Processes ◽  
Time Resolved ◽  
Temperature Electron

ABSTRACTThe physical processes occurring during the initial stages of ultrafast laser heating of metals are described. Femtosecond laser irradiation is used to create nonequilibrium heating in metals. In such a nonequilibrium state, the electron temperature can be heated up to a few thousand degrees above the lattice temperature. Electron-lattice relaxation is time-resolved in copper and found to be 1 – 4 ps depending on the laser heating ffuence. The technique of time-resolved electron diffraction (a lattice structural and temperature probe) is described. Utilization of this technique for lattice temperature measurement of thin metal films is demonstrated.

Raman Scattering with Nanosecond Resolution During Pulsed Laser Heating of Silicon

1982 ◽  
Vol 13 ◽  
Author(s):  
D. Von Der Linde ◽  
G. Wartmann ◽  
A. Ozols
Keyword(s):  
Phase Transition ◽  
Raman Scattering ◽  
Laser Heating ◽  
Crystalline Silicon ◽  
Silicon Crystal ◽  
Pulsed Laser ◽  
Lattice Temperature ◽  
Time Resolved ◽  
Pulsed Laser Heating ◽  
Anti Stokes

ABSTRACTWe present time-resolved measurements of spontaneous anti-Stokes and Stokes Raman scattering during pulsed laser heating of crystalline silicon. The time-evolution of the lattice temperature is determined from the measured anti-Stokes/Stokes intensity ratio. In a separate calibration experiment we measure the temperature dependence of the anti-Stokes/Stokes ratio of an oven-heated silicon crystal from 300 K up to 900 K. The phase transition occuring during laser heating is detected by monitoring the changes of the optical reflectivity during laser irradiation. Our data suggest that the phase transition occurs at a lattice temperature of ∼600 K.

Dynamics of Ultrafast Laser Induced Damage in Single Crystal Ni-based Superalloy During Machining

2006 ◽  
Vol 980 ◽  
Author(s):  
Joel P. McDonald ◽  
Shuwei Ma ◽  
John A. Nees ◽  
Tresa M. Pollock ◽  
Steven M. Yalisove
Keyword(s):  
Shock Wave ◽  
Laser Fluence ◽  
Ultrafast Laser ◽  
Laser Exposure ◽  
Mechanical Shock ◽  
Incident Laser ◽  
Machining Time ◽  
Time Resolved ◽  
Pump Probe ◽  
Laser Induced Damage

AbstractPump-probe imaging of femtosecond pulsed laser ablation was performed to investigate the mechanical shock induced on an intermetallic superalloy CMSX-4 during femtosecond laser machining. Time resolved shadowgraphic images were collected of the shock wave produced in the air above the target following laser exposure (0-10.3 nanoseconds). The dimensions of the shock wave were measured as a function of delay time and laser fluence (1.27 J/cm2 - 62.8 J/cm2). Time-resolved shadowgraphic images of the ablation event will be presented, and the corresponding damage morphology as a function of incident laser fluence will be discussed.

Time-Resolved IR Video Imaging with Synchronized Scanned Laser Heating

1988 ◽  
pp. 496-499 ◽  
Author(s):  
P. K. Kuo ◽  
I. C. Oppenheim ◽  
L. D. Favro ◽  
Z. J. Feng ◽  
R. L. Thomas ◽  
...  
Keyword(s):  
Laser Heating ◽  
Time Resolved ◽  
Video Imaging

FRET Study Between Carbon Quantum Dots and Malachite Green by Steady-State and Time-Resolved Fluorescence Spectroscopy

2020 ◽  
Vol 10 (3) ◽  
pp. 178-188
Author(s):  
Bipin Rooj ◽  
Ankita Dutta ◽  
Debojyoti Mukherjee ◽  
Sahidul Islam ◽  
Ujjwal Mandal
Keyword(s):  
Quantum Dots ◽  
Energy Transfer ◽  
Fluorescence Spectroscopy ◽  
Malachite Green ◽  
Dye Degradation ◽  
Fluorescence Emission ◽  
Carbon Quantum Dots ◽  
Time Resolved Fluorescence ◽  
Physical Processes ◽  
Time Resolved

Background: Understanding the interaction between different organic dyes and carbon quantum dots helps us to understand several photo physical processes like electron transfer, energy transfer, molecular sensing, drug delivery and dye degradation processes etc. Objective: The primary objective of this study is to whether the carbon quantum dots can act as an electron donor and can participate in the different photo physical processes. Methods: In this work, Carbon Quantum Dots (CQDLs) are synthesized in most economical and simple carbonization method where petals of Nelumbo nucifera L. are used as a carbon precursor. The synthesized CQDLs were characterized by using experimental techniques like UV−Vis absorption, FT-IR, Transmission Electron Microscopy (TEM), steadystate and time-resolved fluorescence spectroscopy. Results: The spectral analysis shows that the so synthesized CQDLs are spherical in shape and its diameter is around 4.2 nm. It shows the fluorescence emission maximum at 495 nm with a quantum yield of 4%. In this work the interaction between Carbon Quantum Dots (CQDLs) and an organic dye Malachite Green (MG) is studied using fluorescence spectroscopic technique under ambient pH condition (At pH 7). The quenching mechanism of CQDLs with MG was investigated using Stern-Volmer equation and time-resolved fluorescence lifetime studies. The results show that the dominant process of fluorescence quenching is attributed to Forster Resonance Energy Transfer (FRET) having a donor acceptor distance of 53 Å where CQDLs act as a donor and MG acts as an acceptor. Conclusion: This work has a consequence that CQDLs can be used as a donor species for different photo physical processes such as photovoltaic cell, dye sensitized solar cell, and also for antioxidant activity study.

Nonlinearity and time-resolved studies of ion emission in ultrafast laser ablation of graphite

2008 ◽  
Vol 92 (4) ◽  
pp. 999-1004 ◽  
Author(s):  
A. Kaplan ◽  
M. Lenner ◽  
C. Huchon ◽  
R. E. Palmer
Keyword(s):  
Laser Ablation ◽  
Ultrafast Laser ◽  
Time Resolved ◽  
Ion Emission ◽  
Ultrafast Laser Ablation

UlTRAFAST LATTICE RELAXATION DYNAMICS OF EXCITON IN A QUAISI-1-D METAL-HALOGEN COMPLEX

2001 ◽  
Vol 15 (28n30) ◽  
pp. 3965-3968
Author(s):  
ATSUSHI SUGITA ◽  
TAKASHI SAITO ◽  
TAKAYOSHI KOBAYASHI ◽  
MASAHIRO YAMASHITA
Keyword(s):  
Wave Packet ◽  
Free Exciton ◽  
Mixed Valence ◽  
Lattice Relaxation ◽  
Relaxation Dynamics ◽  
Time Resolved ◽  
Pump And Probe ◽  
Probe Spectroscopy ◽  
Electronic Ground ◽  
The Ideal

A quasi-one-dimensional halogen-bridged mixed-valence metal complex is studied by time-resolved pump and probe spectroscopy with sub-5 fs time resolution. Two kinds of oscillatory signals are observed, which are attributed to the wave packet motions both in an electronic ground state and in a self-trapped exciton (STE) state. The onset of the wave packet motion is found to be delayed by about 50 fs, comparing with the ideal wave packet in the electronic excited state. The delay reflects the thermalization process in a free exciton (FE) state and a lattice relaxation process from FE to STE states.

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