Basic concepts and methods

Nonlinear optics deals with optical phenomena, caused by the interaction of applied electromagnetic fields to molecules or materials with emission of new electromagnetic fields which differ in frequency, phase, or other physical properties from the incident ones [1-3]. This kind of optical phenomena are related to the polarizability of a molecule or of a bulk material. 

When a bulk material is subjected to an oscillating external electric field produced by an incident radiation, there is a polarization effect, expressed by 

instead of a bulk material, the applied electromagnetic field is interacting with a molecule, the induced polarizatimi is expressed by 

The second-order NLO properties are of interest for a variety of NLO processes [1-3]. One of the most relevant is the SHG, originated by the mixing of three waves two incident waves with frequency co interact with the molecule or the bulk material with NLO properties, defined by a given value of the quadratic hyperpolarizability, fi, or of the second-order electrical susceptibility, respectively, to produce a new electrical wave, named SH, of frequency 2co. Another important second-order NLO process is the electrooptic Pockels effect which requires the presence of an external d.c. electric field, E(0), in addition to the optical E co) electrical field. This effect produces a change in the refractive index of a material proportional to the applied electric field, and can be exploited in devices such as optical switches and modulators [1-3]. 

To obtain molecular or bulk materials displaying significant second-order NLO effects, high values of jS or of respectively, are required. In the case of molecules, in 1977 Oudar gave a theoretical interpretation of the electronic factors controlling [20,21]. The quadratic hyperpolarizability of a molecule is originated 

---

This section describes briefly some of the basic concepts and methods of automatic 3D model builders. However, interested readers are referred to Chapter II, Section 7.1 in the Handbook, where a more detailed description of the approaches to automatic 3D structure generation and the developed program systems is given. 

Chemical Thermodynamics Basic Concepts and Methods, Seventh Edition. By Irving M. Klotz and Robert M. Rosenberg... 

We present the basic concepts and methods for the measurement of infrared and Raman vibrational optical activity (VOA). These two forms of VOA are referred to as infrared vibrational circular dichroism (VCD) and Raman optical activity (ROA), respectively The principal aim of the article is to provide detailed descriptions of the instrumentation and measurement methods associated with VCD and ROA in general, and Fourier transform VCD and multichannel CCD ROA, in particular. Although VCD and ROA are closely related spectroscopic techniques, the instrumentation and measurement techniques differ markedly. These two forms of VOA will be compared and the reasons behinds their differences, now and in the future, will be explored. 

To convey the basic concepts and methods of quantum mechanics that describe the discrete energy levels and the statistical behavior of microscopic systems... 

P. Glue, R. P. Clement (1999) Cytochrome P450 enzymes and drug metabolism—basic concepts and methods of assessment. Cell Mol Neurobiol, 19, 309-323. 

KLO 08] Klotz I.M., Rosenberg R.W., Chemical Thermodynamics Basic Concepts and Methods, 7th ed., Wiley Sons, New York, 2008. 

It is hard to find out the most appropriate equipment/method and performance index to measure and assess the quality of catalysts, which is difficult in unified definition and standardization of methods. So far, some methods for evaluating the activities of a few catalysts such as those for catalytic ammonia synthesis and catalytic cracking have been standardized. The evaluation methods are different due to the varieties of catalysts and the experiences of researchers. Sometimes, the technical details of evaluation methods are a part of patent, such as formula and preparation process is confidential. Even then, some basic conceptions and methods for the evaluation and testing of catalysts are still worthy being introduced, which is the main focus of this chapter. 

Since the publication of the first edition, little has changed as far as the basic concepts and methods of plastics testing. What has changed is the manner in which the data is collected and analyzed. Since the advent of computers and digital instruments, data collection and subsequent analysis and interpretation have become much simpler and faster. 

F. S. Tyner, J. R. Knott, and W. B. Mayer, Fundemantals of EEG Technology. Vol. 1. Basic Concepts and Methods. New York Raven Press, 1983... 

---