Speaker
Description
A few years after the invention of lasers, it was found that focusing a pulsed laser beam into a gas causes dielectric breakdown of the gas in a consistent part of the converging beam. The process is called laser-induced dielectric breakdown (LIDB) while the phenomenon is usually called a laser spark. Although the physical nature of laser sparks is the subject of numerous reviews (results of early investigations are summarized in refs [1-3]), their chemical consequences have been reviewed only rarely. A systematic study of chemical reactions initiated by laser sparks was conducted by Ronn’s group at CUNY in the 70s and 80s (see for example [4]; a review of early laser-plasma-chemical experiments is given in refs [5,6]). Their motivation for performing such experiments was the preparation of well-defined fine particles [4]. The research on LIDB-initiated chemical reactions of this kind has been triggered again recently by the ad¬vent of nanotechnologies. The systematic part of this contribution describes the laser-plasma-chemical behaviour of simple inorganic gases and their mixtures, metal carbonyls and organometallics, and organic vapours. Laser ignition of fuel mixtures is a deeply investigated branch of laser-plasma chemistry because of numerous commercial and military interests.
Figure 1. Optical photographs of laser sparks generated at atmospheric pressure by (A,B) high-power iodine photodissociation laser (wavelength = 1.3152 m, pulse energy of 85 J behind the entrance window of the cell, pulse duration = 350 ps (FWHM); the NIR laser beam was focused by a glass lens of 25 cm focal length; the LIDB plasma is in the figure B circled) [7].
However, the strongest impulses for studying the laser-plasma chemistry come currently from astrophysics, astrochemistry and astrobiology, where laser sparks have been used as a laboratory model of high-energy-density phenomena (e.g., cometary impact, lightning, meteor flight and related phenomena) in planetary atmospheres and other objects in the Space. Utilization of a single pulse from a high-power laser system for creation of large laser sparks (see Fig. 1 [7]) is discussed. The particular processes responsible for the chemical action of a laser spark are identified and described in detail. Although this contribution is primarily focused on laser-plasma chemistry in homogeneous molecular gases, chemical consequences of LIDB in liquids (laser cavitation) and on liquid-solid and gas-solid interfaces (especially those related to meteor flight phenomena [8]) are reported as well.
Recent results (see for example refs [8-11]) of Space science motivated interaction experiments performed at the PALS (Prague Asterix Laser System) facility are presented and discussed in this talk.
References
1. C. DeMichelis: Laser induced gas breakdown: A bibliographical review, IEEE J. Quant. Electron. QE-5, 188 (1969).
2. J. F. Ready: Effects of High-Power Laser Radiation (Academic Press, New York-London, 1971), p. 212.
3. Yu. P. Raizer: Laser Induced Discharge Phenomena (Consultants Bureau, New York, 1977).
4. A. M. Ronn: Particulate formation induced by infrared laser dielectric breakdown, Chem. Phys. Lett. 42, 202 (1976).
5. D. Babánková, S. Civiš, L. Juha: Chemical consequences of laser-induced breakdown in molecular gases, Prog. Quant. Electron. 30, 75 (2006).
6. L. Juha, S. Civiš: Laser-plasma chemistry: Chemical reactions initiated by laser-produced plasmas, In: Lasers in Chemistry (Ed. M. Lackner), Vol. 2 (Wiley-VCH, Weinheim, 2008), p. 899.
7. S. Civiš, L. Juha, D. Babánková, J. Cvačka, O. Frank, J. Jehlička, B. Králiková, J. Krása, P. Kubát, A. Muck, M. Pfeifer, J. Skala, J. Ullschmied: Amino acid formation induced by high-power laser in CO2/CO-N2-H2O gas mixtures, Chem. Phys. Lett. 386, 169 (2004).
8. M. Ferus, P. Kubelík, L. Petera, L. Lenža, J. Koukal, A. Křivková, V. Laitl, A. Knížek, H. Saeidfirozeh, A. Pastorek, T. Kalvoda, L. Juha, R. Dudžák, S. Civiš, E. Chatzitheodoridis, M. Krůs: Main spectral features of meteors studied using a terawatt-class high-power laser, Astronom. Astrophys. 630, A127 (2019).
9. P. B. Rimmer, M. Ferus, I. P. Waldmann, A. Knížek, D. Kalvaitis, O. Ivanek, P. Kubelík, S. N. Yurchenko, T. Burian, J. Dostál, L. Juha, R. Dudžák, M. Krůs, J. Tennyson, S. Civiš, A. T. Archibald, A. Granville-Willett: Identifiable acetylene features predicted for young Earth-like exoplanets with reducing atmospheres undergoing heavy bombardment, Astrophys. J. 888, 21 (2020).
10. E. Mohammadi, L. Petera, H. Saeidfirozeh, A. Knizek, P. Kubelik, R. Dudzak, M. Krus, L. Juha, S. Civis, R. Coulon, O. Malina, J. Ugolotti, V. Ranc, M. Otyepka, J. Sponer, M. Ferus, J. E. Sponer: Formic acid, a ubiquitous but overlooked component of the early Earth atmosphere, Chem.-Eur. J. 26, 12075 (2020).
11. A. N. Heays, T. Kaiserová, P. B. Rimmer, A. Knížek, L. Petera, S. Civiš, L. Juha, R. Dudžák, M. Krůs, M. Scherf, H. Lammer, R. Pascal, M. Ferus: Nitrogen oxide production in laser-induced breakdown simulating impacts on the Hadean atmosphere, J. Geophys. Res. – Planets 127, e2021JE006842 (2022).
Acknowledgements
The author and his co-workers greatly appreciate a financial support of the PALS facility operation and development provided by the Czech Ministry of Education, Youth and Sports (CMEYS) and the European Commission (EC) (grant nr. LM2018114). The Czech Science Foundation (GAČR) funded research projects nr. GA19-03314S and GA17-05076S related to the issue reported in this talk.