Photoemission Spectroscopy: Fundamental Aspects
Over the past five decades, photoemission has become one of the most popular spectroscopies for investigating matter in its various aggregation states. It finds its application in fields ranging from solid state physics to chemistry, biology and geology,
- PDF / 2,168,438 Bytes
- 43 Pages / 439.37 x 666.142 pts Page_size
- 114 Downloads / 256 Views
Photoemission Spectroscopy: Fundamental Aspects Carlo Mariani and Giovanni Stefani
Abstract Over the past five decades, photoemission has become one of the most popular spectroscopies for investigating matter in its various aggregation states. It finds its application in fields ranging from solid state physics to chemistry, biology and geology, just to mention a few. The number of researchers who need to be introduced to this field is ever increasing, and the spectrum of backgrounds that they possess is very large. Aim of this chapter is to provide for all of them a basic introduction to the models upon which photoemission is based and, by the help of simple examples, to explain what information photoemission can provide.
9.1 Introduction An electron bound to an atom, a molecule or a solid, is characterized by energy, momentum and spin quantum numbers. Among other spectroscopic techniques, photoemission is the best suited tool to study these physical quantities. It is based upon the photoelectric effect, one of the cornerstones on which quantum mechanics description of matter rests. In essence, the photoelectron effect amounts to shining a monochromatic electromagnetic radiation (hν) on a sample and producing free electrons with a well-defined energy spectrum. The Einstein equation connects energy of the quantum of the electromagnetic field (photon) with the maximum energy of the ejected free electron (EeMAX ) through a constant characteristic of the sample C. Mariani Dipartimento di Fisica, CNISM, Università di Roma “La Sapienza”, Piazzale Aldo Moro 2, 00185 Rome, Italy e-mail: [email protected] G. Stefani (B) Dipartimento di Scienze, Università Roma Tre and CNISM Unità Roma 3, Via della Vasca Navale 84, 00146 Rome, Italy e-mail: [email protected] S. Mobilio et al. (eds.), Synchrotron Radiation, DOI: 10.1007/978-3-642-55315-8_9, © Springer-Verlag Berlin Heidelberg 2015
275
276
C. Mariani and G. Stefani
(work function ) EeMAX = hν − . It establishes a close relationship between sample characteristics and energy spectrum of the ejected electrons and suggests using the photoemission process to build up a wide range of different spectroscopies aimed at studying the electronic structure of matter in its various aggregation states. Such a spectroscopy allows investigation of the occupied electronic states, it gives information on the dielectric (insulator, semiconductor or metal) and chemical state, on the magnetic properties and on the local structure. Although the photoelectron effect is known since over a century [1–6], spectroscopies based upon this phenomenon [7, 8] have developed over the past fifty years, mostly driven by progresses in development of monochromatic, bright and tunable light sources [9, 10]. Nowadays, photoelectron spectroscopy (PES) has practical applications in many fields of science, such as surface physics and chemistry, material science, nano technologies and still significantly contributes to the understanding of fundamental aspects of physics, chemistry, biology, etc.
Data Loading...
