Energy spectrum of photoelectrons produced by picosecond laser-induced surface multiphoton photoeffect

Farkas, Gy.; Tóth, Cs.

doi:10.1103/physreva.41.4123

Cited by 51 publications

(23 citation statements)

References 26 publications

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“…The Coulomb repulsion within a short electron bunch as, for instance, generated in a photoemission process by an ultrashort light pulse, can distort the energy distribution of the electrons and result in a considerable loss in both spectral resolution and angular resolution [90][91][92][93][94][95]. Figure 21.12 illustrates the extent to which the effect of Coulomb interaction, also referred to as space charging, can affect the (angle-resolved) photoelectron spectral distribution.…”

Section: Space Charge Effectsmentioning

confidence: 99%

Time‐Resolved Photoelectron Spectroscopy at Surfaces Using Femtosecond XUV Pulses

Mathias¹,

Bauer²,

Aeschlimann³

et al. 2010

Dynamics at Solid State Surfaces and Interfaces

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Laser-based femtosecond light sources in the infrared, visible, and the nearultraviolet spectral regime have been successfully employed for a large number of experimental studies of real-time dynamics of ultrafast surface processes, as is discussed at length in the preceding chapters. Visible and near-ultraviolet wavelengths, however, are capable of probing only a relatively restricted range of energies in the surface electronic structure -specifically electronic states within a few electron volts around the Fermi energy. Most of the surface-related time-resolved photoemission studies to date are, for instance, based on a two-photon photoemission process (the first (static) two-photon photoemission work was performed by Teich et al. [1]) and focus on the ultrafast dephasing and decay of electronic excitations in this optical energy range [2]. The use of femtosecond pulsed light sources in the extreme ultraviolet (XUV) 1) spectral region, in contrast, allows direct access to much more deeply bound electronic levels. Furthermore, the range of electron momentum that can be studied can be substantially expanded by the use of these light sources. Both aspects are highly attractive in the study of ultrafast processes since they provide new and relevant system information, for instance, on the chemical or magnetic state, or the structure, of a surface -information that is often not accessible in time-resolved experiments employing sources at lower photon energy.The first experimental work showing that ultrafast light sources in the XUV and soft X-ray region of the spectrum were possible were conducted in the late 1980s. Studies by McPherson et al. [3] and Ferray et al. [4] were the first to clearly show the 1) The extreme ultraviolet regime covers the wavelength between 50 and 1 nm (20-1200 eV).

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Section: Space Charge Effectsmentioning

confidence: 99%

Time‐Resolved Photoelectron Spectroscopy at Surfaces Using Femtosecond XUV Pulses

Mathias¹,

Bauer²,

Aeschlimann³

et al. 2010

Dynamics at Solid State Surfaces and Interfaces

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“…High-energy electrons have been observed in ps laser interaction with solids. Electron velocities of the order of 10 9 cm s −1 have been reported in such instances [22]. Another heating mechanism, as mentioned above, is that due to the absorption of the laser radiation through inverse bremsstrahlung [30].…”

Section: Tof Profiles Of Electronsmentioning

confidence: 99%

“…Probe current for the first electron temporal peak as a function of laser intensity. The electron current increases up to a laser intensity of about 9.5 × 10 10 W cm −2 and then saturates due to plasma shielding surface and volume photoelectric effects through multiphoton excitation of metallic surfaces have been reported [22][23][24] and in such cases the electron current density (J) has a power law dependence on the input laser intensity (I). That is, J ∝ I n where n is an integer such that nhν (h is Planck's constant and ν the light frequency) coincides with or slightly exceeds the work function of the material.…”

Section: Tof Profiles Of Electronsmentioning

confidence: 99%

Prompt electron emission and collisional ionization of ambient gas during pulsed laser ablation of silver

Issac¹,

Varier²,

Gopinath³

et al. 1998

Applied Physics A: Materials Science & Processing

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Abstract.A silver target kept under partial vacuum conditions was irradiated with focused nanosecond pulses at 1.06 µm from a Nd:YAG laser. The electron emission monitored with a Langmuir probe shows a clear twin-peak distribution. The first peak which is very sharp has only a small delay and it indicates prompt electron emission with energy as much as 60 ± 5 eV. Also the prompt electron emission shows a temporal profile with a width that is same as that for the laser pulse whereas the second peak is broader, covers several microseconds, and represents the low-energy electrons (2 ± 0.5 eV) associated with the laser-induced silver plasma as revealed by time-of-flight measurements. It has been found that prompt electrons ejected from the target collisionally excite and ionize ambient gas molecules. Clearly resolved rotational structure is observed in the emission spectra of ambient nitrogen molecules. Combined with time-resolved spectroscopy, the prompt electrons can be used as excitation sources for various collisional excitation-relaxation experiments. The electron density corresponding to the first peak is estimated to be of the order of 10 17 cm −3 and it is found that the density increases as a function of distance away from the target. Dependence of probe current on laser intensity shows plasma shielding at high laser intensities. 52.50.J; 52.40.N; 52.75.R; 34.80.D; 39.90 With the invention of the high-power pulsed lasers, the study of laser-matter interactions has assumed many new dimensions among which the phenomenon of laser ablation has a major role both in fundamental studies and in technological applications [1][2][3][4]. The interaction of laser radiation with solids is a very complex process. It includes light absorption and plasma formation in the vicinity of the target [5], thermalisation of the ablation products due to collisions among themselves and with ambient gas molecules [6-9], evolution and propagation of the plume [10-13], gas phase chemical reactions [14,15], and the eventual deposition of the ablative products on suitable substrates situated at a distance from the target [1,2]. In metals, laser absorption occurs within the skin depth because of the exponential attenuation of electromagnetic radiation in a conducting medium. The light is primarily absorbed by electrons present within the skin depth through inverse bremsstrahlung leading to rapid ionization before significant ablation of the solid occurs. The absorbed energy is transferred to the lattice through electron-phonon (e-ph) interactions which usually happens within a few picoseconds after the absorption [16]. The e-ph relaxation time increases with the laser fluence. This increase in e-ph relaxation time is due to the greater difference between electron and lattice temperatures and hence the greater number of collisions that are required for thermalisation. Most of the theoretical and observational models on laser ablation describe the formation of the plasma and its gas dynamic effects. Consequently, the hot-electron emissio...

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“…Kylstra (2001)), and considers the inelastic electron scattering on the oscillating double-layer potential generated by the incoming laser field at the metal surface. The model has already been succesfully used to interpret the experimental results on very high order surface photoelectric effect in the near infrared (Farkas & Tóth (1990)) and in the far infrared regime (Farkas et al, 1998). In this description the basic interaction leading to very high nonlinearities is caused by the collective velocity field of the oscillating electrons near the metal surface, within a layer of thickness smaller that the penetration depth δ.…”

Section: Classical Description Of Basic Strong Field Phenomena Carrimentioning

confidence: 99%

“…In case of multiphoton photoelectric effect of metals, Farkas & Tóth (1990) and Farkas et al (1998) measured very high-order above-threshold electrons coming from metal targets. The theoretical interpretation of these results has been first given by the present author in and recently in Kroó et al (2007).…”

Section: Classical Description Of Basic Strong Field Phenomena Carrimentioning

confidence: 99%

Intensity Effects and Absolute Phase Effects in Nonlinear Laser-Matter Interactions

Varró¹

2010

Laser Pulse Phenomena and Applications

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Energy spectrum of photoelectrons produced by picosecond laser-induced surface multiphoton photoeffect

Cited by 51 publications

References 26 publications

Time‐Resolved Photoelectron Spectroscopy at Surfaces Using Femtosecond XUV Pulses

Time‐Resolved Photoelectron Spectroscopy at Surfaces Using Femtosecond XUV Pulses

Prompt electron emission and collisional ionization of ambient gas during pulsed laser ablation of silver

Intensity Effects and Absolute Phase Effects in Nonlinear Laser-Matter Interactions

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