The photoemission filmed in 3D and in real time

Albert Einstein’s interpretation of the photoelectric effect in 1905 revolutionized basic and applied science. Researchers have obtained the first experimental 3D film of this ultra-fast process in weather (Time is a concept developed by human beings to apprehend the…) real and at the atomic level.

Photoemission, interpreted in 1905 by Albert Einstein (Albert Einstein (born March 14, 1879 in Ulm, Württemberg, and died on…) like issuing a electron (The electron is an elementary particle of the lepton family, and has a charge…) by the matter (Matter is the substance that makes up any body having a tangible reality. Its…) following theabsorption (In optics, absorption refers to the process by which the energy of a photon is taken up…) of one quantum (In physics, a quantum (Latin word meaning “how much” and which is written…) of light (Light is the set of electromagnetic waves visible to the eye…) (the photon), played a key role in the development of Quantum mechanics (Quantum mechanics is the branch of physics that aims to study and… at the beginning of the XX^thcentury (A century is now a period of a hundred years. The word comes from the Latin saeculum, i, which…). Today she has become a tool (A tool is a finalized object used by a living being in order to increase its…) extremely powerful analysis of matter using sources of radiation (Radiation, synonymous with radiation in physics, designates the process of emission or…) varied, from lasers to synchrotrons, ranging from UV to X-rays.

The process of photoemission occurs on such short time scales – on the order of billionths of billionths of second (Second is the feminine of the adjective second, which comes immediately after the first or which…) (1 attosecond = 10^-18 s) – that it has until recently been inconceivable to directly observe its dynamic (The word dynamic is often used to designate or qualify what relates to movement. It…), yet essential to its full understanding. Indeed, it is during the process that the spectroscopic signatures specific to each species (In the life sciences, the species (from the Latin species, « type »…) chemical are transferred to the photoelectron, as it leaves theatom (An atom (Ancient Greek ἄτομος [atomos] » that…)the molecule (A molecule is an electrically neutral chemical assembly of at least two atoms, which…) where the material (A material is a material of natural or artificial origin that man shapes…), everything (The whole understood as the whole of what exists is often interpreted as the world or…) continuing to feel the influence of the ion core.

It was in 2001 that the first sources of coherent light pulses of « attosecond » durations saw the day (The day or the day is the interval which separates the sunrise from the sunset; it is the…) [1]. The availablity (The availability of a piece of equipment or a system is a measure of performance that we…) of these sources with hitherto unpublished properties marked the advent of time-resolved spectroscopy at the attosecond scale, the ultimate scale of the dynamics occurring in chemical matter, and remaining, to this day, the shortest that can be experimentally resolved. Attosecond spectroscopy has since proven itself by demonstrating the possibility of exploring the dynamics of a variety of fundamental processes, among which photoemission [2].

In this context, a collaboration involving teams from the CEA, Sorbonne (The Sorbonne is a monumental complex in the Latin Quarter of Paris. It takes its name from…) University (A university is an institution of higher education whose objective is the…)Paris-Saclay University, Lyon 1 University and CNRS(1) combined an attosecond interferometric approach with a photoelectron detection method called « d’imagery (Imagery is primarily the making and trading of physical images that…) of speed (We distinguish 🙂 » in order to access, for the first time, the complete dynamics of photoemission as a function of the direction of emission (2). The experiments carried out at CEA Paris-Saclay, on the new ATTOLab platform, focused on the photoemission of I’helium (Helium is a noble gas or rare gas, practically inert. With atomic number 2, it…) two-photon, involving the anisotropic intermediate states 1s3p and 1s4p. The measurements of the modulus and the phase (The word phase can have several meanings, it is used in several fields and…) of the’amplitude (In this simple wave equation:) of photoionization could be analyzed and interpreted thanks to numerical simulations and analytical developments carried out at Sorbonne University. The revealed dynamics, as well as their angular dependencies, differ significantly depending on the degree (The word degree has several meanings, it is notably used in fields…) implication of intermediate states, illustrating the richness of the phenomena involved (see figure). These results are published in the journal Science Advances.

This approach exclusively experimental (In art, these are creative approaches based on questioning dogmas…)making it possible to « film » photoemission at the atomic scale, is applicable to a wide range of chemical species at rest or participating in a reaction, promising to reveal the secrets of the electronic correlations and dynamics governing the structure and transformations of matter.

3D film of the photoemission of a helium atom following the simultaneous absorption of an extreme photon ultraviolet (Ultraviolet (UV) radiation is electromagnetic radiation with a length…) (XUV) and a photon (In particle physics, the photon (often symbolized by the letter γ — gamma)…) infrared (Infrared (IR) radiation is electromagnetic radiation with a wavelength…) (IR). L’moment (The instant designates the smallest constituent element of time. The instant is not…) t = 0 is placed at the maximum of the recovery (A covering of a set X is a set P of non-empty subsets of X such that the union…) XUV + IR pulses. Each snapshot represents the complex magnitude of the rate ofionization (Ionization is the action of removing or adding charges to an atom or a…) (module in polar coordinates (Polar coordinates are, in mathematics, a coordinate system…)phase data (In information technologies, a datum is an elementary description,…) by the color code). At the beginning and at the end of theinteraction (An interaction is an exchange of information, affects or energy between two agents within…)the emission of electrons takes place preferentially in the direction z of the polarization (the polarization of electromagnetic waves; the polarization due to moments…) XUV/IR. Remarkably, at the maximum of the interaction with light, near time 0, the interferences between the ionization pathways involving the 1s3p and 1s4p intermediate states strongly affect the symmetry (Generally the term symmetry refers to the existence, in a…) of the emission, which is then mostly perpendicular to the polarization of the radiation.

Laboratories:

– Interactions, dynamics and lasers laboratory (LIDYL, CNRS/CEA);
– Laboratory of physical chemistry (Physical chemistry is the study of the physical bases of chemical systems and… – matter and radiation (LCPMR, CNRS/Sorbonne Univ.);
– Institute (An institute is a permanent organization created for a certain purpose. It is…) molecular sciences at Orsay (ISMO, CNRS/Univ. Paris-Saclay);
– Light and Matter Institute (ILM, CNRS/Univ. de Lyon 1).

References:

[1] Observation (Observation is the action of attentive follow-up of phenomena, without the will to see them…) of a Train (A train is a guided vehicle running on rails. A train is composed of…) of Attosecond Pulses from High Harmonic Generation, PM Paul, ES Toma, P. Breger, G. Mullot, F. Augé, Ph. Balcou, HG Muller and P. Agostini, Science (Science (Latin scientia, « knowledge ») is, according to the dictionary…) 292, 1689 (2001).
DOI: 10.1126/science.1059413

[2] Attosecond dynamics through a Fano resonance: monitoring the birth of a photoelectron, V. Gruson, L. Barreau, À. Jiménez-Galan, F. Risoud, J. Caillat, A. Maquet, B. Square (A square is a regular polygon with four sides. This means that its…), F. Lepetit, JF. Hergott, T. Ruchon, L. Argenti, R. Taïeb, F. Martin and P. Salières, Science 354, 734 (2016).
DOI: 10.1126/science.aah5188

[3] Anisotropic dynamics of two-photon ionization: An attosecond movie of photoemission, A. Autuori, D. Platzer, M. Lejman, G. Gallician, L. Maëder, A. Covolo, L. Bosse, M. Dalui, D. Bresteau, J.-F. Hergott, O. Tcherbakoff, HJB Marroux, V. Loriot, F. Lépine, L. Fish (In the classical classification, fish are aquatic vertebrate animals…)R. Taïeb, J. Caillat and P. Salières, Science Advances 8, 12 (2022).
DOI: 10.1126/sciadv.abl7594