Computer Simulation of Laser Ablation of Molecular Systems

The interaction of laser pulses with organic matter leading to massive material removal (ablation) from a target is a subject of scientific as well as applied interest.  Important practical applications include laser surgery, matrix-assisted laser desorption/ionization (MALDI) of biomolecules for mass - spectrometric investigations and surface microfabrication of polymer thin films.  We have developed a molecular level model for computer simulation of laser ablation of organic solids.

The following are the main results of the simulations to date.

• The microscopic mechanisms of laser ablation are delineated.  The laser induced pressure buildup and the phase explosion due to overheating of the irradiated material are identified as the key processes that determine the dynamics of laser ablation. See Fig. 1 (13K), Refs. 1, 2 and 10.
• The fluence threshold behavior in laser ablation is predicted.  The physics of the material removal below and above threshold is analyzed. See Fig. 2 (12K) and Refs. 2 and 10.
• A series of large scale simulations are performed in the regime of thermal confinement that is characteristic for UV-MALDI conditions. The total ablation yield and plume composition are related to the mechanisms of ejection and to the available experimental data. The drastic increase of the total yield at the ablation threshold is found to be imperceptible in the fluence dependence of the monomer yield measured in mass spectrometry experiments. See Fig. 12 (6K), Fig. 13 (4K), and Ref. 10.
• An expression for the analytical description of the velocity distribution of molecules ejected in laser ablation is proposed based on the simulation results. See Fig. 3 (28K), Fig. 4 (24K), Ref. 3.
• Conditions for desorption of large analyte molecules in MALDI are studied.  The existence of the fluence threshold for the ejection of analytes, high kinetic energies and weak mass dependence of the ejection velocities on the molecular mass as well as the conditions that provide survivability of large fragile biomolecules in MALDI are addressed. See animated sequence of ablation events (114K), Fig. 11 (27K), Fig. 12 (36K), Refs. 5 and 7.
• Mechanisms of laser damage in the case when the laser energy is deposited within spatially localized absorbers embedded into a transparent medium are studied and related to the experimental observations for pigmented tissues. A strong pulse width dependence of the threshold energy for producing a visible damage to the absorbing granule and the mechanism of the damage is observed. The acoustic impedance mismatch at the interface between the absorbing granule and the surrounding medium is found to define the role of the intragranular fracturing in short pulse laser damage.  See Fig. 5 (11K), Fig. 6 (18K), Fig. 7 (4K), Fig. 8 (14K), Fig. 9 (20K), Fig. 10 (9K), Refs. 4 and 6.
• A dynamic boundary condition is developed to account for the laser induced pressure wave propagation through the boundary of the computational cell as well as for the direct laser energy deposition in the boundary region. The boundary condition allows us to focus the computational effort of the MD simulation to the region where active processes of laser induced melting, ablation and damage occur.   See Fig. 14 (10K), Fig. 15 (12K), and Refs. 11 and 12.
• A combined molecular dynamics - finite element method has been implemented and tested on the propagation of the laser induced pressure wave through a micrometer-sized sample. This computational approach can be useful in cases where a detailed atomic-level analysis is necessary in localized spatially separated regions of a large system.  See Fig. 16 (6K), Ref. 8.
• A series of large-scale MD simulations of laser ablation and damage performed in two different irradiation regimes, stress confinement and thermal confinement. An analysis of the microscopic mechanisms of laser ablation is combined with a systematic investigation of the interrelation between the different parameters of the ablation process accessible for experimental investigation, including the fluence dependence of the total and monomer yields, cluster composition of the ablation plume, velocity and angular distributions of ejected molecules, profiles of the acoustic waves propagating from the absorption region.  See animated sequences of snapshots from the simulations and Ref. 14. New.

Publications

1. L. V. Zhigilei, P. B. S. Kodali, and B. J. Garrison, Molecular Dynamics Model for Laser Ablation of Organic Solids, J. Phys. Chem. B 101, 2028-2037, 1997.
   Abstract, Full Text: PDF (1.1 MB)
2. L. V. Zhigilei, P. B. S. Kodali, and B. J. Garrison, On the Threshold Behavior in the Laser Ablation of Organic Solids, Chem. Phys. Lett. 276, 269-273, 1997.
   Abstract, Full Text: PDF (116 kB)
3. L. V. Zhigilei and B. J. Garrison, Velocity Distributions of Molecules Ejected in Laser Ablation, Appl. Phys. Lett. 71, 551-553, 1997.
   Abstract, Full Text: PDF (78 kB), GZipped PS (597 kB)
4. L. V. Zhigilei and B. J. Garrison, Computer Simulation Study of Damage and Ablation of Submicron Particles from Short Pulse Laser Irradiation, Applied Surface Science 127-129, 142-150, 1998.
   Abstract, Full Text: PDF (593 kB)
5. L. V. Zhigilei, P. B. S. Kodali, and B. J. Garrison A Microscopic View of Laser Ablation, J. Phys. Chem. B, Feature Article, 102, 2845-2853, 1998.
   Abstract, Full Text: PDF (181 kB)
6. L. V. Zhigilei and B. J. Garrison, Microscopic Simulation of Short Pulse Laser Damage of Melanin Particles, in Laser-Tissue Interaction IX, S.L.Jacques, Editor, Proc. SPIE 3254, 135-143, 1998.
   Abstract, Full Text: PDF (1.2 MB)
7. L. V. Zhigilei and B. J. Garrison, Velocity Distributions of Analyte Molecules in Matrix-assisted Laser Desorption from Computer Simulations, Rapid Commun. Mass Spectrom. 12, 1273-1277, 1998.
   Abstract, Full Text: PDF (406 kB)
8. J. A. Smirnova, L. V. Zhigilei, and B. J. Garrison, A combined molecular dynamics and finite element method technique applied to laser induced pressure wave propagation, Comput. Phys. Commun. 118, 11-16, 1999.
   Abstract, Full Text: PDF (114 kB)
9. P. B. S. Kodali, L. V. Zhigilei, and B. J. Garrison, Phase Transition at Low Fluences in Laser Desorption of Organic Solids: A Molecular Dynamics Study, Nucl. Instrum. Methods Phys. Research B 153, 167-171, 1999.
   Abstract, Full Text: PDF (114 kB)
10. L. V. Zhigilei and B. J. Garrison, Molecular dynamics simulation study of the fluence dependence of particle yield and plume composition in laser desorption and ablation of organic solids, Appl. Phys. Lett. 74, 1341-1343, 1999.
    Abstract, Full Text: PDF (82 kB), GZipped PS (670 kB)
11. L. V. Zhigilei and B. J. Garrison, Pressure waves in microscopic simulations of laser ablation, in Multiscale Modelling of Materials, edited by T. Diaz de la Rubia, T. Kaxiras, V. Bulatov, N.M.Ghoniem, and R. Phillips, (Mat. Res. Soc. Symp. Proc. 538), 491-496, 1999.
    Abstract, Full Text: PDF (1 MB)
12. L. V. Zhigilei and B. J. Garrison, Mesoscopic Breathing Sphere Model for Computer Simulation of Laser Ablation and Damage, in Proceedings of the International Conference on Modeling and Simulation of Microsystems, Semiconductors, Sensors, and Actuators (MSM'99), (Computational Publications: Boston), 138-141, 1999.
    Abstract, Full Text: PDF (44 kB), PS (736 kB)
13. L. V. Zhigilei and B. J. Garrison, Mechanisms of Laser Ablation from Molecular Dynamics Simulations: Dependence on the Initial Temperature and Pulse Duration, Appl. Phys. A 69, S75-S80, 1999.
    Abstract, Full Text: PDF (453 kB)
14. L. V. Zhigilei and B. J. Garrison, Microscopic Mechanisms of Laser Ablation of Organic Solids in the Thermal and Stress Confinement Irradiation Regimes, J. Appl. Phys. 88, 1281-1298, 2000.
    Abstract, Full Text: PDF (800 kB)
15. T. A. Schoolcraft, G. S. Constable, L. V. Zhigilei, and B. J. Garrison, Molecular Dynamics Simulation of the Laser Disintegration of Aerosols Particles, Anal. Chem., Accelerated Article, 72, 5143-5150, 2000.
    Abstract, Full Text: PDF (433 kB)
16. T. A. Schoolcraft, G. S. Constable, B. Jackson, L. V. Zhigilei, and B. J. Garrison, Molecular Dynamics Simulations of Laser Disintegration of Amorphous Aerosol Particles with Spatially Nonuniform Absorption, Nucl. Instr. Meth. B 180, 245-250, 2001.
    Abstract, Full Text: PDF (365 kB)
17. Y. G. Yingling, L. V. Zhigilei, B. J. Garrison, A. Koubenakis, J. Labrakis, S. Georgiou, Laser Ablation of Bi-component Systems: A Probe of Molecular Ejection Mechanisms, Appl. Phys. Lett. 78, 1631-1633, 2001.
    Abstract, Full Text: PDF (163 kB)
18. Y. G. Yingling, L. V. Zhigilei, B. J. Garrison, Photochemical Fragmentation Processes in Laser Ablation of Organic Solids, Nucl. Instr. Meth. B 180, 171-175, 2001.
    Abstract, Full Text: PDF (97 kB)
19. T. E. Itina, L. V. Zhigilei, B. J. Garrison, Matrix Assisted Pulsed Laser Evaporation of Polymeric Materials: Molecular Dynamic Simulation, Nucl. Instr. Meth. B 180, 238-244, 2001.
    Abstract, Full Text: PDF (303 kB)
20. Y. Dou, L. V. Zhigilei, Z. Postawa, N. Winograd, and B. J. Garrison, Thickness effects of water overlayer on its explosive evaporation at heated metal surfaces, Nucl. Instr. Meth. B 180, 105-111, 2001.
    Abstract, Full Text: PDF (374 kB)
21. Y. Dou, L. V. Zhigilei, N. Winograd, and B. J. Garrison, Explosive Boiling of Water Films Adjacent to Heated Surfaces: A Microscopic Description, J. Phys. Chem. A 105, 2748-2755, 2001.
    Abstract, Full Text: PDF (1.18 MB)
22. G. J. Williams, L. V. Zhigilei, and B. J. Garrison, Laser Ablation in a Model Two-phase System, Nucl. Instr. Meth. B 180, 209-215, 2001.
    Abstract, Full Text: PDF (1.1 MB)
23. A. G. Zhidkov, L. V. Zhigilei, A. Sasaki, and T. Tajima, Short-laser-pulse Driven Emission of Energetic Ions into a Solid Target from a Surface Layer Spalled by a Laser Prepulse, Appl. Phys. A, in press, 2001.
    Abstract, Full Text: PDF (796 kB)
24. Y. G. Yingling, L. V. Zhigilei, B. J. Garrison, The Role of Photochemical Fragmentation in Laser Ablation: A Molecular Dynamics Study, Journal of Photochemistry and Photobiology, in press, 2001.
    Abstract
25. L. V. Zhigilei, B. J. Garrison, M. Goto, J. Hobley, M. Kishimoto, H. Fukumura, and A. G. Zhidkov, The Role of Inertial and Spatial Confinement in Laser Interaction with Organic Materials, -in: Proceedings of the 5th World Multi-Conference on Systemics, Cybernetics and Informatics (SCI 2001 / ISAS 2001), (Institute of Informatics and Systemics: Orlando, Florida), 215-220, 2001.
    Abstract, Full Text: PDF (719 kB)
26. L. V. Zhigilei, Computational Model for Multiscale Simulation of Laser Ablation, -in: Advances in Materials Theory and Modeling-Bridging Over Multiple-Length and Time Scales, edited by V. V. Bulatov, F. Cleri, L. Colombo, L. J. Lewis, N. Mousseau, (Mat. Res. Soc. Symp. Proc. 677), invited paper, in press, 2001.
    Abstract, Full Text: PDF (486 kB)
27. M. Goto, L. V. Zhigilei, J. Hobley, M. Kishimoto, B. J. Garrison, and H. Fukumura, Laser Expulsion of an Organic Molecular Nano-jet from a Confined Domain onto a Polymer Surface, J. Appl. Phys., in press, 2001.
    Abstract
28. T. E. Itina, L. V. Zhigilei, and B. J. Garrison, Microscopic Mechanisms of Matrix Assisted Laser Desorption of Analyte Molecules: Insights from Molecular Dynamics Simulation, J. Phys. Chem. B, submitted, July 2001.
    Abstract
29. L. V. Zhigilei, Y. G. Yingling, T. E. Itina, T. A. Schoolcraft, and B. J. Garrison, Molecular Dynamics Simulations of Matrix Assisted Laser Desorption - Connections to Experiment, Int. J. Mass Spectrom., submitted, August 2001.
    Abstract