Estimation of electron temperature in heated metallic nanoparticle

A method is proposed for determining the temperature of hot electrons in a metallic nanoparticle embedded in a dielectric matrix under ultrashort laser pulses irradiation. The amplitude and power of the longitudinal spherical acoustic oscillations as functions of density and elastic properties of...

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Date:2017
Main Author: Grigorchuk, N.I.
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Language:English
Published: Інститут фізики конденсованих систем НАН України 2017
Series:Condensed Matter Physics
Online Access:http://dspace.nbuv.gov.ua/handle/123456789/157028
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Cite this:Estimation of electron temperature in heated metallic nanoparticle / N.I. Grigorchuk // Condensed Matter Physics. — 2017. — Т. 20, № 4. — С. 43703: 1–7. — Бібліогр.: 22 назв. — англ.

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spelling irk-123456789-1570282019-06-20T01:28:22Z Estimation of electron temperature in heated metallic nanoparticle Grigorchuk, N.I. A method is proposed for determining the temperature of hot electrons in a metallic nanoparticle embedded in a dielectric matrix under ultrashort laser pulses irradiation. The amplitude and power of the longitudinal spherical acoustic oscillations as functions of density and elastic properties of the medium, the laser pulse duration, the electron temperature, radii of particles, and the electron-phonon coupling constant are obtained. The efficiency of the electron energy transfer from heated noble nanoparticles to a surrounding environment is estimated for different electron temperatures. Запропоновано метод визначення температури гарячих електронiв в металевiй наночастинцi, що знаходиться в середовищi пiд дiєю ультракоротких лазерних iмпульсiв. Одержанi амплiтуда i потужнiсть поздовжних сферичних акустичних коливань як функцiя густини i пружних властивостей середовища, тривалостi лазерного iмпульсу, радiусу частинки, електрон-фононної константи зв’язку та електронної температури. Зроблено оцiнку ефективностi передачi енергiї електронiв вiд пiдiгрiтих благородних наночастинок в оточуюче їх середовище за рiзних температур електронiв. 2017 Article Estimation of electron temperature in heated metallic nanoparticle / N.I. Grigorchuk // Condensed Matter Physics. — 2017. — Т. 20, № 4. — С. 43703: 1–7. — Бібліогр.: 22 назв. — англ. 1607-324X PACS: 78.67.Bf, 68.49.Jk, 73.23.-b, 52.25.Os, 36.40.Vz DOI:10.5488/CMP.20.43703 arXiv:1712.05355 http://dspace.nbuv.gov.ua/handle/123456789/157028 en Condensed Matter Physics Інститут фізики конденсованих систем НАН України
institution Digital Library of Periodicals of National Academy of Sciences of Ukraine
collection DSpace DC
language English
description A method is proposed for determining the temperature of hot electrons in a metallic nanoparticle embedded in a dielectric matrix under ultrashort laser pulses irradiation. The amplitude and power of the longitudinal spherical acoustic oscillations as functions of density and elastic properties of the medium, the laser pulse duration, the electron temperature, radii of particles, and the electron-phonon coupling constant are obtained. The efficiency of the electron energy transfer from heated noble nanoparticles to a surrounding environment is estimated for different electron temperatures.
format Article
author Grigorchuk, N.I.
spellingShingle Grigorchuk, N.I.
Estimation of electron temperature in heated metallic nanoparticle
Condensed Matter Physics
author_facet Grigorchuk, N.I.
author_sort Grigorchuk, N.I.
title Estimation of electron temperature in heated metallic nanoparticle
title_short Estimation of electron temperature in heated metallic nanoparticle
title_full Estimation of electron temperature in heated metallic nanoparticle
title_fullStr Estimation of electron temperature in heated metallic nanoparticle
title_full_unstemmed Estimation of electron temperature in heated metallic nanoparticle
title_sort estimation of electron temperature in heated metallic nanoparticle
publisher Інститут фізики конденсованих систем НАН України
publishDate 2017
url http://dspace.nbuv.gov.ua/handle/123456789/157028
citation_txt Estimation of electron temperature in heated metallic nanoparticle / N.I. Grigorchuk // Condensed Matter Physics. — 2017. — Т. 20, № 4. — С. 43703: 1–7. — Бібліогр.: 22 назв. — англ.
series Condensed Matter Physics
work_keys_str_mv AT grigorchukni estimationofelectrontemperatureinheatedmetallicnanoparticle
first_indexed 2025-07-14T09:22:16Z
last_indexed 2025-07-14T09:22:16Z
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fulltext Condensed Matter Physics, 2017, Vol. 20, No 4, 43703: 1–7 DOI: 10.5488/CMP.20.43703 http://www.icmp.lviv.ua/journal Estimation of electron temperature in heated metallic nanoparticle N.I. Grigorchuk Bogolyubov Institute for Theoretical Physics of the National Academy of Sciences of Ukraine, 14-b Metrologichna St., 03680 Kyiv, Ukraine Received May 12, 2017, in final form June 19, 2017 A method is proposed for determining the temperature of hot electrons in a metallic nanoparticle embedded in a dielectric matrix under ultrashort laser pulses irradiation. The amplitude and power of the longitudinal spherical acoustic oscillations as functions of density and elastic properties of the medium, the laser pulse duration, the electron temperature, radii of particles, and the electron-phonon coupling constant are obtained. The efficiency of the electron energy transfer from heated noble nanoparticles to a surrounding environment is estimated for different electron temperatures. Key words: electron temperature, metal nanoparticle, ultrashort laser pulses PACS: 78.67.Bf, 68.49.Jk, 73.23.-b, 52.25.Os, 36.40.Vz 1. Introduction Metallic nanoparticles (MNs) are mainly studied due to their unique optical properties [1] and extensive practical applications [2–5]. Over the last decade, the acoustic oscillations of MNs excited by ultrashort laser pulses have been under intense study [1–9]. This is due to the availability of important data relating to the elastic properties of these particles and their mechanical coupling to the surrounding medium, which forms the foundation for the design of elasticity sensors in the nanometer range [10]. The generation of sound waves byMNs was originally observed experimentally for noble nanoparticles [2–4]. When MNs are excited by ultrashort pulses, the energy pulse is initially transferred to the gas of free electrons which collide with one another as well as with the lattice vibrations, and redistribute this energy (being thermalized) over a short time (of the order of tens of picoseconds in a 100 Å particle [3]). The electron gas in the particle is immediately heated. Due to a low heat capacity of the electron gas (compared to the lattice), there originates a short (but strong) electron pressure burst [11]. It is equivalent to a short mechanical impact upon the particle surface over an infinitely small time interval and can generate spherical sound waves in the medium surrounding the particle [12, 13]. In this article, we proposed a method for determining the temperature of hot electron gas in a metallic nanoparticle embedded in a dielectric matrix under ultrashort laser pulses irradiation. To accomplish this, the amplitude and power of the longitudinal sound wave generated by the excess pressure of an electron gas inside the MN driven by ultrashort laser pulses are calculated. So far, this problem has been little studied theoretically. 2. Initial principles and model Let an ultrashort laser pulse of duration τ0 be incident on a spherical MN embedded in an infinite, elastically isotropic, dielectric medium. Energy transfer from the laser to the lattice of a nanoparticle depends much on the relationship between the particle sizes, the electron mean free path in the particle, and the Debye length lD = πυF/ωD, which plays an important role in the energy exchange between the hot This work is licensed under a Creative Commons Attribution 4.0 International License . Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. 43703-1 https://doi.org/10.5488/CMP.20.43703 http://www.icmp.lviv.ua/journal http://creativecommons.org/licenses/by/4.0/ N.I. Grigorchuk electrons and the lattice [14]. Its values for several metals are listed below in table 2. We shall consider here the particles with radii R < lD/2. The additional pressure that develops during heating of the electron gas by the laser pulse can produce oscillations of the nanoparticle surface, which in turn, generate longitudinal acoustic waves in the elastically isotropic space around the particle. The equation for the propagation of longitudinal acoustic oscillations in this space is given by [15] ∇2uL(t) − 1 s2 L ∂2 ∂t2 uL(t) = 0, (2.1) where sL is the longitudinal sound speed in the medium. Elastic displacement waves uL are accompanied by bulk compressions and expansions of the surrounding medium. As boundary conditions for equation (2.1), we take a condition that all forces applied to the particle surface (r = R) are equal to zero. This equality can be presented as [15][ σrr − 2Es R2 ur (t) ] ���� r=R = −δp(t). (2.2) Here, ur = |ur | is the radial component of the displacement, R is the particle radius, Es is the surface energy density, δp(t) is the time dependent additional pressure of the hot electrons, and σrr is the stress tensor, whose components are expressed through the moduli K , µ of the uniform compression and rigidity, which one can find elsewhere (e.g., in [15]). For spherical acoustic oscillations, one can assume that uL(t) = ur (t). The pressure of the electron gas on the surface of the nanoparticle can be written as the sum p(t) = p0 + δp(t). (2.3) Here, the first term represents the pressure of a degenerate Fermi gas at Te = 0 K, p0 = 2 5 nµ0, where n = N/V is the electron density, V is the particle volume, and µ0 is the limiting value of the chemical potential at Te = 0 K (µ0 = εF, where εF is the Fermi energy). The second term, δp(t), represents the additional time dependent gas pressure owing to the electron mobility at temperatures Te > 0. It can be written as [16] δp(t) = αT2 e (t), α = π2 6 n k2 B µ0 . (2.4) 3. Amplitude of the sound wave To solve equation (2.1) with the boundary condition (2.2), we use the potential method [15] u(r, t) ≡ ∇∇∇ϕ(r, t). Then, representing of function ϕ(r, t) in the form of spherical waves expanding from particle center ϕ(r, t) = φ ( t − (r − R)/sL ) /r , where φ is an arbitrary, twice differentiable function and using the boundary condition (2.2) at the nanoparticle surface, we found for φ an inhomogeneous differential equation ∂2 ∂t2 φ(t) + 2γ ∂ ∂t φ(t) + ω2 0 φ(t) = −δp(t) R ρ , (3.1) in which ρ is the mass density of the medium surrounding the nanoparticle, and γ = 1 sLR ( 2s2 T + Es ρR ) , ω2 0 = 2 R2 ( 2s2 T + Es ρR ) . (3.2) Here, sT is a transverse sound speed [15]. The parametersω0 and γ are the oscillator eigenfrequency in the absence of friction and the damping decrement, respectively. Note that when a solid medium surrounds the nanoparticle, we must set Es = 0 in expressions (3.2). However, if the nanoparticle is embedded in a liquid medium, then only the second terms in expressions (3.2) must be retained. The quantity 1/γ specifies the time over which the oscillations are completely damped. It depends on the nanoparticle radius [17]. 43703-2 Estimation of electron temperature in heated metallic nanoparticle Equation (3.1) formally describes the motion of the oscillator under the action of an external driving force of the form δp(t)R/ρ. We will consider that there are no oscillator eigenmodes without an external force, and that they are generated only by an external force. If the driving force acting on the oscillator, for example, is δ-shaped δp(t) = pimδ(t − τ0), (3.3) then the solution of equation (3.1) with the initial conditions φ = 0 and φ′ = −Rpim/ρ for t = τ0 is given by φ(t) = −e−γ(t−τ0) sin [ω(t − τ0)] Rpim/ρω, (3.4) where ω = √ ω2 0 − γ 2 0 , provided that ω0 > γ. When the time dependence of the function Te(t) is known, the value of pim can be determined explicitly. Comparing expressions (2.4) and (3.3), we find α ∞∫ 0 T2 e (t − τ0) dt = pim . (3.5) The variation of the electron temperature with time can be modelled or determined analytically. Let us suppose that initially (at t = τ0) the oscillator is not displaced, i.e., is at rest, and obeys the initial conditions φ(τ0) = 0 and φ′(τ0) = 0. Then, the solution of equation (3.1) for an arbitrary form of the driving force can be presented in an integral form [18] φ(t) = − Re−γt ρω t∫ τ0 δp(τ) eγτ sin [ω(t − τ)] dτ, (3.6) with the conditions that δp(τ) , 0 and t > 0. Equation (3.6) easily answers the question of how the oscillator behaves after an excess pressure δp(τ) has acted on it over a short time interval (τ0, τ1). The upper limit in equation (3.6) for this case, evidently, will be the quantity τ1. Then, using the mean-value theorem in equation (3.6), we obtain φ(t) = −RIe−γteγξτ1 sin(ωt)/ρω, (3.7) where τ0/τ1 < ξ < 1, while ∫τ1 τ0 δp(τ)dτ ≡ I presents the impulse of the excess pressure of the electron gas. If ω0τ1ξ � 2π, then the explicit form of δp(τ) is not essential; an important point is only the value of I. When ω0 � γ, the maximum displacement umax caused by the excess pressure “impact”, with using potential method and equation (3.7), will be umax = I/ρω0R. (3.8) Taking into account here equation (3.2) for the case Es = 0, we obtain umax, Es=0 = I/2 √ µρ, (3.9) i.e., the magnitude of umax, Es=0 is independent of the particle radius (and is more independent since the rigidity modulus and mass density of the nanoparticle are smaller). On the other hand, if the Es > 0, then a dependence on the particle radius shows up, and the magnitude of umax is decreased as R is reduced. The maximum displacement over the time τ1 − τ0 with account for the finite damping, has the form: umax, Es=0 = I(1 − Rγ/sL) 2√µρ √ 1 − (sT/sL)2 e−γ(τ1−τ0). (3.10) Therefore, it is possible to determine the pressure impulse I by measuring the maximum displacement of the physical object. 43703-3 N.I. Grigorchuk 4. Power radiated by nanoparticle surface A certain part of the accumulated byMN’s energy is carried away from the particle into the surround- ing matrix by sound waves. The instantaneous elastic energy flux from the surface of the sphere (for the case of Es = 0) can be calculated using a formula [19] W(t) = S δp(t) υr (R, t). (4.1) Here, S is the area of the particle surface and υr is the radial or vibrational velocity. In terms of time, conventionally, two stages in this process can be identified: one is an impetuous rise in δp during an ultrashort time spell (t ∼ τ0) and another one is a slower decrease (under t > τ0) owing to a transfer of the electron energy to the surrounding matrix. The dependence of the δp(t) within the second time spell, can be well described by expression (2.4). In order to take an explicit account of the behavior of the pressure in the initial time spell, the function δp(t) can be presented as the product of two functions, δp(t) → θ(t − τ0) · αT2 e (t), (4.2) where we use equation (2.4), while θ(t − τ0) is the Heaviside unit-step function that specifies the pressure behavior when t → τ0. Let us also suppose that the electron temperature varies with time in accordance with the rule Te(t) = Te(τ0) e−β(t−τ0), β = gR Ce , Ce = 3αTe , (4.3) whereCe ≡ Ce ( Te(τ0) ) is the heat capacity of the electron gas, which depends on the electron temperature taken at the instant of time t = τ0. The electron-phonon coupling constant in equation (4.3) can be computed from the formula gR = 27 16 n m α kB 1 ρpR ( π~ a )3 ( U1 A )2 . (4.4) Here, a is the lattice constant for the MN, ρp denotes the mass density of the MN, U1 is the energy required to detatch the first electron from the neutral unexcited atom, and A refers to the electron work function of the metal. Formula (4.4) follows from equation (115) of the work [20] using the equation (2.4) and the following relationships ωD ' √ σ ρp ( π a )3 , υF = ~ m ( 3nπ2)1/3 , (4.5) where ωD is the Debye frequency and σ is the surface energy density. Taking into account equations (4.2) and (4.3), after integratingwith respect to τwithin limits 0 < τ < t and some transformations, we finally obtain W(t) = 4πR2 ρsL δp(t) δpm(t) ω2 0 + 4β(β − γ) ( − 2β ( sL R − 2β ) + e(2β−γ)t0 { [ ω2 0 + 2β ( sL R − 2γ )] cos (ωt0) + [ (ω2 0 − 2βγ) ( sL R − γ ) − 2βω2 ] sin (ωt0) ω }) , (4.6) where t0 = t − τ0. Equation (4.6) gives the energy per unit time carried out by spherical sound waves from the nanoparticle into the surrounding medium. The analysis show that the power of the sonic signalW(t) is of the form of damped oscillations. The number of oscillations depends much on the density of the matrix material. The amplitude of the sound power is increased with an increase in the radius of MN, and it is fully damped over longer times. For different metals (but with the same radius) the amplitude ofW(t) will be greater for MNs with a higher coupling constant gR. The maximum power of the acoustic signal is reached at the time instant t0 = 0. From equation (4.6), it is equal to Wmax �� t0=0 = 4πR2[δp(τ0)] 2/ρsL. (4.7) 43703-4 Estimation of electron temperature in heated metallic nanoparticle The temperature decrease of the electron gas is proportional to the product βTe, which characterizes the cooling rate of the electron gas. Since the fall of the electron temperature occurs much more slowly than the electron’s heating, we can assume that the influence of this mechanism on the sound power is negligible in the first approximation. Formally, this allows us to direct β → 0 in equation (4.6). In this case, the sound signal will correspond to exponentially damped oscillations. The time dependence of the excess pressure in the case of β → 0, can also be estimated using the equation δp(t) �� β→0 ≈ −2gR t Te(τ0)/3, (4.8) which follows from the energy balance equation for the electrons. The maximum power of the signal [equation (4.7)], with the account for approximation (4.8), is Wmax �� t=τ0, β→0 = 16 9 π ρsL [gR τ0 R Te(τ0)] 2, (4.9) where the dependence on the laser pulse duration appears explicitly. 5. Total energy of the oscillations of the metal nanoparticle We now determine the total energy transferred from the pulsating spherical surface to the surrounding matrix. We will consider the case β , 0, when the powerW(t) is given by equation (4.6). Integrating equation (4.6) with respect to time over the interval 0 < t < ∞, in view of expressions (2.4) and (3.2) at Es = 0, we obtain E = ∞∫ τ0 W(t) dt = 2πR ρsL sL + 2βR ω2 0 + 4β(β + γ) α2T4 e . (5.1) Equation (5.1) shows that the total energy is proportional to the fourth power of the electron temperature. In the case β = 0, it is easy to reveal that this energy depends on the volume of the particle and is reciprocal to the rigidity modulus of the medium. On the other hand, the work necessary to shift the spherical surface at the maximal distance umax [defined by equation (3.10)], is E = 8πRu2 maxαT2 e . (5.2) Comparing it with equation (5.1), one finds Te = 2umax √ ρsL α ω2 0 + 4β(β + γ) sL + 2βR . (5.3) Another way to determine Te is as follows. The total energy obtained by the electron gas in the MN is Etot = 3VαT2 e /2. (5.4) The efficiency of the energy transfer η from the pulsating spherical MN to the sound oscillations can be estimated taking the ratio of equations (5.1) and (5.4). It has the simplest form in the case β→ 0 η(T) ≡ E |β→0/Etot = αT2 e /4µ. (5.5) The temperature dependence of η(T) for noble nanoparticles embedded in a plexiglass matrix is plotted in figure 1. The calculations were done using equations (5.1) and (5.4), with account for the characteristics both of the matrix and the MNs given in tables 1 and 2. The efficiency increases as the square of the temperature. Actually, it increases if the rigidity modulus of the medium in which the nanoparticle is embedded gets smaller. So, knowing from experiment the efficiency η, it is easy to estimate the electron temperature in MN. The highest possible ηT for noble metal nanoparticles with R = 100 Å embedded in a plexiglass matrix are presented in table 2 at Te = 104. 43703-5 N.I. Grigorchuk 0 2000 4000 6000 8000 10 000 0 10 20 30 40 Te Η H% L Figure 1. (Color online) Dependence of the sound signal power efficiency on electron temperature for Cu nanoparticle (solid curve), Ag (dashed curve), and Au (dotted curve), embedded in plexiglass. Table 1. Constants for the plexiglass [21]. Medium K µ ρ sL sT (dyn/cm2) (dyn/cm2) (g/cm3) (cm/s) (cm/s) Plexiglass 5.83·1010 1.48·1010 1.18 2.57 ·105 1.12·105 Table 2. Physical parameters of the noble MNs. Metal lD (Å) α ( erg cm3 K2 ) n ( cm−3) [22] η104 (%) Cu 1197 235.5 8.45 · 1022 39.5 Ag 1552 208.35 5.85 · 1022 35.15 Au 1968 208.9 5.90 · 1022 35.3 6. Conclusions Themethod has been proposed for the estimation of hot electron temperature in metallic nanoparticles embedded in a dielectric matrix under irradiation of ultrashort laser pulses. Analytic expressions have been derived for the amplitude and power of longitudinal spherical sound oscillations as function of the density and elastic properties of the medium, the laser pulse duration, electron temperature, nanoparticle radius, and electron-phonon coupling constants. The maximal displacement of any oscillator in the MN’s material is due to the “impact” of the excess pressure of the electron gas. The magnitude of the sound signal power at the moment of the laser pulse ending can be used to estimate the maximal electron temperature in the MN. The latter is determined by the cooling rate of the electron gas and the rate of its pressure change. The efficiency with which the energy of the hot electrons is carried away by sound oscillations has been examined for the noble metals. It has been shown that the sound energy transfer efficiency is considerably higher in the medium with smaller rigidity moduli. Acknowledgements Author is indebted to DFFD of Ukraine for single financial support of this work. 43703-6 Estimation of electron temperature in heated metallic nanoparticle References 1. Bohren C.F., Huffman D.R., Absorption and Scattering of Light by Small Particles, Wiley & Sons, Weinheim, 2004. 2. Crut A., Maioli P., Del Fatti N., Vallée F., Chem. Soc. Rev., 2014, 43, 3921, doi:10.1039/C3CS60367A. 3. Hodak J.H., Martini I., Hartland G.V., J. Chem. Phys., 1998, 108, 9210, doi:10.1063/1.476374. 4. Thibodeaux C.A., Kulkarni V., Chang W.-S., Neumann O., Cao Y., Brinson B., Ayala-Orozco C., Chen C.-W., Morosan E., Link S., Nordlander P., Halas N.J., J. Phys. Chem. B, 2014, 118, 14056, doi:10.1021/jp504467j. 5. Alabastri A., Tuccio S., Giugni A., Toma A., Liberale C., Das G., De Angelis F., di Fabrizio E., Zaccaria R.P., Materials, 2013, 6, 4879, doi:10.3390/ma6114879. 6. Jiang L., Tsai H.-L., Int. J. Heat Mass Transfer, 2007, 50, 3461, doi:10.1016/j.ijheatmasstransfer.2007.01.049. 7. Karpov V.G., Nardone M., Grigorchuk N.I., Phys. Rev. B, 2012, 86, 075463, doi:10.1103/PhysRevB.86.075463. 8. Grigorchuk N.I., Tomchuk P.M., Phys. Rev. B, 2009, 80, 155456, doi:10.1103/PhysRevB.80.155456. 9. Grigorchuk N.I., Condens. Matter Phys., 2013, 16, 33706, doi:10.5488/CMP.16.33706 . 10. Dissanayake D.W. (Ed.), Acoustic Waves, Sciyo, Rijeka, 2000. 11. Perner M., Gresillon S., MÜarz J., von Plessen G., Feldmann J., Porstendorfer J., Berg K.-J., Berg G., Phys. Rev. Lett., 2000, 85, 792, doi:10.1103/PhysRevLett.85.792. 12. Voisin C., Christofilos D., Loukakos P.A., Del Fatti N., Vallée F., Lermé J., GaudryM., Cottancin E., PellarinM., Broyer M., Phys. Rev. B, 2004, 69, 195416, doi:10.1103/PhysRevB.69.195416. 13. Plech A., Kotaidis V., LorencM.,WulffM., Chem. Phys. Lett., 2005, 401, 565, doi:10.1016/j.cplett.2004.11.072. 14. Hartland G.V., Annu. Rev. Phys. Chem., 2006, 57, 403, doi:10.1146/annurev.physchem.57.032905.104533. 15. Landau L.D., Lifshitz E.M., Theory of Elasticity, Pergamon Press, New York, 1986. 16. Koroljuk S., Mel’nychuk S., Val’ O., Fundamentals of Statistical Physics and Thermodynamics, Knygy-XXI, Chernivtsi, 2004, (in Ukrainian). 17. Halté V., Bigot J.-Y., Palpant B., Broyer M., Prével B., Pérez A., Appl. Phys. Lett., 1999, 75, 3799, doi:10.1063/1.125460. 18. Kamke E., Differentialgleichungen: Lösungsmetoden und Lösungen, Teubner, Stuttgart, 1983. 19. Fedorov F.I., Theory of Elastic Waves in Crystals, Plenum Press, New York, 1968. 20. Fedorovich R.D., Naumovets A.G., Tomchuk P.M., Phys. Rep., 2000, 328, 73, doi:10.1016/S0370-1573(99)00094-0. 21. Lide D.R. (Ed.), CRC Handbook of Chemistry and Physics, 92th Ed., CRC Press, Boca Raton, 2011. 22. Kittel Ch., Introduction to Solid State Physics, Wiley & Sons, New York, 2005. Визначення температури електронiв у пiдiгрiтiй металевiй наночастинцi М.I. Григорчук Iнститут теоретичної фiзики iм.М.М. Боголюбова НАН України, вул.Метрологiчна, 14-б, 03680 Київ, Україна Запропоновано метод визначення температури гарячих електронiв в металевiй наночастинцi, що зна- ходиться в середовищi пiд дiєю ультракоротких лазерних iмпульсiв. Одержанi амплiтуда i потужнiсть поздовжних сферичних акустичних коливань як функцiя густини i пружних властивостей середовища, тривалостi лазерного iмпульсу, радiусу частинки, електрон-фононної константи зв’язку та електронної температури. Зроблено оцiнку ефективностi передачi енергiї електронiв вiд пiдiгрiтих благородних нано- частинок в оточуюче їх середовище за рiзних температур електронiв. Ключовi слова: електронна температура, металева наночастинка, ультракороткi лазернi iмпульси 43703-7 https://doi.org/10.1039/C3CS60367A https://doi.org/10.1063/1.476374 https://doi.org/10.1021/jp504467j https://doi.org/10.3390/ma6114879 https://doi.org/10.1016/j.ijheatmasstransfer.2007.01.049 https://doi.org/10.1103/PhysRevB.86.075463 https://doi.org/10.1103/PhysRevB.80.155456 https://doi.org/10.5488/CMP.16.33706 https://doi.org/10.1103/PhysRevLett.85.792 https://doi.org/10.1103/PhysRevB.69.195416 https://doi.org/10.1016/j.cplett.2004.11.072 https://doi.org/10.1146/annurev.physchem.57.032905.104533 https://doi.org/10.1063/1.125460 https://doi.org/10.1016/S0370-1573(99)00094-0 Introduction Initial principles and model Amplitude of the sound wave Power radiated by nanoparticle surface Total energy of the oscillations of the metal nanoparticle Conclusions