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Electron thermalization and relaxation in laser-heated nickel by few-femtosecond core-level transient absorption spectroscopy

Chang, Hung-Tzu and Guggenmos, Alexander and Cushing, Scott K. and Cui, Yang and Din, Naseem Ud and Acharya, Shree Ram and Porter, Ilana J. and Kleineberg, Ulf and Turkowski, Volodymyr and Rahman, Talat S. and Neumark, Daniel M. and Leone, Stephen R. (2021) Electron thermalization and relaxation in laser-heated nickel by few-femtosecond core-level transient absorption spectroscopy. Physical Review B, 103 (6). Art. No. 064305. ISSN 2469-9950. doi:10.1103/physrevb.103.064305.

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Direct measurements of photoexcited carrier dynamics in nickel are made using few-femtosecond extreme ultraviolet (XUV) transient absorption spectroscopy at the nickel M_(2,3) edge. It is observed that the core-level absorption line shape of photoexcited nickel can be described by a Gaussian broadening (σ) and a red shift (ω_s) of the ground-state absorption spectrum. Theory predicts and the experimental results verify that after initial rapid carrier thermalization, the electron temperature increase (ΔT) is linearly proportional to the Gaussian broadening factor σ, providing quantitative real-time tracking of the relaxation of the electron temperature. Measurements reveal an electron cooling time for 50 nm thick polycrystalline nickel films of 640±80 fs. With hot thermalized carriers, the spectral red shift exhibits a power-law relationship with the change in electron temperature of ω_s ∝ ΔT^(1.5). Rapid electron thermalization via carrier-carrier scattering accompanies and follows the nominal 4-fs photoexcitation pulse until the carriers reach a quasithermal equilibrium. Entwined with a <6 fs instrument response function, carrier thermalization times ranging from 34 fs to 13 fs are estimated from experimental data acquired at different pump fluences and it is observed that the electron thermalization time decreases with increasing pump fluence. The study provides an initial example of measuring electron temperature and thermalization in metals in real time with XUV light, and it lays a foundation for further investigation of photoinduced phase transitions and carrier transport in metals with core-level absorption spectroscopy.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Chang, Hung-Tzu0000-0001-7378-8212
Guggenmos, Alexander0000-0003-2975-9136
Cushing, Scott K.0000-0003-3538-2259
Din, Naseem Ud0000-0002-7972-4057
Porter, Ilana J.0000-0001-8692-9950
Rahman, Talat S.0000-0003-3889-7776
Neumark, Daniel M.0000-0002-3762-9473
Leone, Stephen R.0000-0003-1819-1338
Additional Information:© 2021 American Physical Society. Received 28 September 2020; revised 7 December 2020; accepted 5 January 2021; published 10 February 2021. The authors would like to thank Xun Shi, Phoebe Tengdin, Wenjing You, and David Prendergast for fruitful discussions. The experimental laboratory work of S.R.L., H.-T. C., and A.G. was supported by the Defense Advanced Research Projects Agency PULSE Program Grant No. W31P4Q-13-1-0017 (concluded), the US Air Force Office of Scientific Research Grants No. FA9550-19-1-0314, No. FA9550-20-1-0334, No. FA9550-15-0037 (concluded), and No. FA9550-14-1-0154 (concluded), the Army Research Office Grant No. WN911NF-14-1-0383, and The W.M. Keck Foundation Award No. 046300-002. H.-T.C. acknowledges support from Air Force Office of Scientific Research (AFOSR) (Grants No. FA9550-15-1-0037 and No. FA9550-19-1-0314) and W. M. Keck Foundation (Grant No. 046300); A.G. acknowledges support from German Research Foundation (Grant No. GU 1642/1-1) and Air Force Office of Scientific Research (AFOSR) (Grants No. FA9550-15-1-0037 and No. FA9550-19-1-0314); S.K.C. acknowledges support by the Department of Energy, Office of Energy Efficiency and Renewable Energy (EERE) Postdoctoral Research Award under the EERE Solar Energy Technologies Office; I.J.P. and S.K.C. acknowledge support from US Department of Energy, Office of Science, Office of Basic Energy Sciences, Materials Sciences and Engineering Division, under Contract No. DEAC02-05-CH11231, within the Physical Chemistry of Inorganic Nanostructures Program (KC3103). N.U.D., S.R.A., V.T. and T.S.R. acknowledge support from U.S. Department of Energy (Grant No. DE-FG02-07ER46354). D.M.N. acknowledges support from the Army Research Office under Grant No. W911NF-20-1-0127 and from US Air Force Office of Scientific Research Grant No. FA9550-15-0037 (concluded).
Funding AgencyGrant Number
Defense Advanced Research Projects Agency (DARPA)W31P4Q-13-1-0017
Air Force Office of Scientific Research (AFOSR)FA9550-19-1-0314
Air Force Office of Scientific Research (AFOSR)FA9550-20-1-0334
Air Force Office of Scientific Research (AFOSR)FA9550-15-0037
Air Force Office of Scientific Research (AFOSR)FA9550-14-1-0154
Army Research Office (ARO)WN911NF-14-1-0383
W. M. Keck Foundation046300-002
Air Force Office of Scientific Research (AFOSR)FA9550-15-1-0037
W. M. Keck Foundation046300
Deutsche Forschungsgemeinschaft (DFG)GU 1642/1-1
Department of Energy (DOE)DE-AC02-05-CH11231
Department of Energy (DOE)DE-FG02-07ER46354
Army Research Office (ARO)W911NF-20-1-0127
Issue or Number:6
Record Number:CaltechAUTHORS:20210318-094013060
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:108477
Deposited By: Tony Diaz
Deposited On:19 Mar 2021 15:43
Last Modified:16 Nov 2021 19:12

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