Photons photoelectric effect

X-ray photoelectron spectroscopy (XPS) is among the most frequently used surface chemical characterization teclmiques. Several excellent books on XPS are available [1, 2, 3, 4, 5, 6 and 7], XPS is based on the photoelectric effect an atom absorbs a photon of energy hv from an x-ray source next, a core or valence electron with bindmg energy is ejected with kinetic energy (figure Bl.25.1) ... 

Photoelectron spectroscopy involves the ejection of electrons from atoms or molecules following bombardment by monochromatic photons. The ejected electrons are called photoelectrons and were mentioned, in the context of the photoelectric effect, in Section 1.2. The effect was observed originally on surfaces of easily ionizable metals, such as the alkali metals. Bombardment of the surface with photons of tunable frequency does not produce any photoelectrons until the threshold frequency is reached (see Figure 1.2). At this frequency, v, the photon energy is just sufficient to overcome the work function

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Phofoelectron spectroscopy is a simple extension of the photoelectric effect involving the use of higher-energy incident photons and applied to the study not only of solid surfaces but also of samples in the gas phase. Equations (8.1) and (8.2) still apply buf, for gas-phase measuremenfs in particular, fhe work function is usually replaced by fhe ionization energy l so fhaf Equation (8.2) becomes... 

Xps is based on the photoelectric effect when an incident x-ray causes ejection of an electron from a surface atom. Figure 7 shows a schematic of the process for a hypothetical surface atom. In this process, an incident x-ray photon of energy hv impinges on the surface atom causing ejection of an electron, usually from a core electron energy level. This primary photoelectron is detected in xps. 

A hundred years ago it was generally supposed that all the properties of light could be explained in terms of its wave nature. A series of investigations carried out between 1900 and 1910 by Max Planck (1858-1947) (blackbody radiation) and Albert Einstein (1879-1955) (photoelectric effect) discredited that notion. Today we consider light to be generated as a stream of particles called photons, whose energy E is given by the equation... 

You can appreciate why scientists were puzzled The results of some experiments (the photoelectric effect) compelled them to the view that electromagnetic radiation is particlelike. The results of other experiments (diffraction) compelled them equally firmly to the view that electromagnetic radiation is wavelike. Thus we are brought to the heart of modern physics. Experiments oblige us to accept the wave-particle duality of electromagnetic radiation, in which the concepts of waves and particles blend together. In the wave model, the intensity of the radiation is proportional to the square of the amplitude of the wave. In the particle model, intensity is proportional to the number of photons present at each instant. 

One of the most direct methods is photoelectron spectroscopy (PES), an adaptation of the photoelectric effect (Section 1.2). A photoelectron spectrometer (see illustration below) contains a source of high-frequency, short-wavelength radiation. Ultraviolet radiation is used most often for molecules, but x-rays are used to explore orbitals buried deeply inside solids. Photons in both frequency ranges have so much energy that they can eject electrons from the molecular orbitals they occupy. 

The new delightful book by Greenstein and Zajonc(9) contains several examples where the outcome of experiments was not what physicists expected. Careful analysis of the Schrddinger equation revealed what the intuitive argument had overlooked and showed that QM is correct. In Chapter 2, Photons , they tell the story that Einstein got the Nobel Prize in 1922 for the explaining the photoelectric effect with the concept of particle-like photons. In 1969 Crisp and Jaynes(IO) and Lamb and Scullyfl I) showed that the quantum nature of the photoelectric effect can be explained with a classical radiation field and a quantum description for the atom. Photons do exist, but they only show up when the EM field is in a state that is an eigenstate of the number operator, and they do not reveal themselves in the photoelectric effect. 

In 1905, Albert Einstein provided an elegant explanation of the photoelectric effect. Einstein postulated that light comes in packets or bundles, called photons. Each photon has an energy that is directly proportional to the... 

Einstein applied the law of conservation of energy to the photoelectric effect, as shown schematically in Figure 7-7. When a metal surface absorbs a photon, the energy of the photon is transferred to an electron ... 

The minimum energy needed to remove an electron from a potassium metal surface is 3.7 X 10 J. Will photons of frequencies 4.3 X 10 s (red light) and of 7.5 X 10 s (blue light) trigger the photoelectric effect If so, what is the maximum kinetic energy of the ejected electrons ... 

Einstein s explanation of the photoelectric effect showed that light has some properties of particles. Light consists of photons, each of which is like a bullet of energy with the discrete energy E = Hy. Although simple, this... 

In the photoelectric effect, energy absorbed from photons provides information about the binding energies of electrons to metal surfaces. When light interacts with free atoms, the interaction reveals information about electrons bound to individual atoms. 

C07-0105. In a photoelectric effect experiment, photons whose energy is 6.00 X 10 J are absorbed by a metal, and the maximum kinetic energy of the resulting electrons is = 2.70 X 10 J. 

XPS is based on the photoelectric effect An atom absorbs a photon of energy hv so that a core or valence electron with binding energy i, is ejected with kinetic energy (Figure 4.6) ... 

Einstein in 1905 who explained the photoelectric effect (He did so by extending an idea proposed by Planck five years earlier to postulate that the energy in a light beam was concentrated in "packets" or photons.. 

Based on the photoelectric effect, electrons in evacuated tubes (photoelectrons) are released from a metal surface if it is irradiated with photons of sufficient quantum energy. These are simple photocells. Photomultipliers are more sophisticated and used in modem spectrophotometers where, via high voltage, the photoelectrons are accelerated to another electrode (dynode) where one electron releases several electrons more, and by repetition up to more than ten times a signal amplification on the order of 10 can be obtained. This means that one photon finally achieves the release of 10 electrons from the anode, which easily can be measured as an electric current. The sensitivity of such a photomultiplier resembles the sensitivity of the human eye adapted to darkness. The devices described are mainly used in laboratory-bound spectrophotometers. 

Photoelectric effect The effect produced when electromagnetic radiation knocks electrons out of a metal. Einstein used this phenomenon to show that light was quantized and came in energy packets called photons. 

The wave interpretation of the interference pattern observed in Young s experiment is inconsistent with the particle or photon concept of light as required by Einstein s explanation of the photoelectric effect. If the monochromatic beam of light consists of a stream of individual photons, then each photon presumably must pass through either slit A or slit B. To test this assertion, detectors are placed directly behind slits A and B and both slits are opened. The light beam used is of such low intensity that only one photon at a time is emitted by S. In this situation each photon is recorded by either one detector or the other, never by both at once. Half of the photons are observed to pass through slit A, half through slit B in random order. This result is consistent with particle behavior. 

When a photon of light hits the surface of a piece of metal, it may, if there is sufficient energy, eject an electron from the metal. Such an electron is called a photoelectron, and the mechanism is known as the photoelectric effect. The diagram at the right shows a setup for measuring the photoelectric effect. 

Albert Einstein s 1905 work on the photoelectric effect paved the way for one of the greatest advances of twentieth-century science, the theory of quantum mechanics. Light had always been regarded as a wave. Quantum mechanics introduced the concept of light being transmitted in wave packets, or photons, that have particle-like qualities as well as wave-like qualities. 

The energy of a photon is now recognized as being proportional to the frequency of the photon. The constant of proportionality relating the photon s frequency and energy is known as Planck s constant. It has a value of 6.626 x 10-34 J s, and is denoted by the letter h. In this activity, you will measure the value of Planck s constant by observing the photoelectric effect. 

Photoelectric Effect—An attenuation process observed for x and gamma radiation in which an incident photon interacts with a tightly bound inner orbital electron of an atom delivering all of its energy to knock the electron out of the atom. The incident photon disappears in the process. 

The photoelectric effect, in which the photon is absorbed and an electron is produced with kinetic energy equal to the difference between the photon energy and the binding energy of the electron (Einstein equation). 

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