Difference between atomic and molecular spectroscopy pdf
Basic Atomic and Molecular Spectroscopy (RSC Publishing) J Michael HollasThe main aim of this unique book is to introduce the student to spectroscopy in a clear manner which avoids, as far as possible, the mathematical aspects of the subject. It is thus intended for first or second year undergraduates, particularly those with minimal mathematics qualifications. After explaining the theory behind spectroscopy, the book then goes on to look at the different techniques, such as rotational, vibrational and electronic spectroscopy. It encompasses both high resolution structural and low resolution analytical spectroscopy, demonstrating their close interrelationship. The many worked problems make this book particularly appealing for independent study. Ideal for the needs of undergraduate chemistry students, Tutorial Chemistry Texts is a major new series consisting of short, single topic or modular texts concentrating on the fundamental areas of chemistry taught in undergraduate science courses. Each book provides a concise account of the basic principles underlying a given subject, embodying an independent-learning philosophy and including worked examples.
Emission and Absorption Spectra
Molecular spectroscopy is the study of absorption of light by molecules. In the gas phase at low pressures, molecules exhibit absorption in narrow lines which are very characteristic of the molecule as well as the temperature and pressure of its environment. In the microwave and long-wavelength infrared regions of the spectrum, these lines are due to quantized rotational motion of the molecule. At shorter wavelengths similar lines are due to quantized vibration and electronic motion as well as rotational motion. The precise frequencies of these lines can be fit to quantum mechanical models which can be used both to determine the structure of the molecule and to predict the frequencies and intensities of other lines. Because this absorption is so characteristic, it is very valuable for detecting molecules in the Earth's stratosphere, planetary atmospheres, and even the interstellar medium.
Spectroscopy is used as a tool for studying the structures of atoms and molecules. The large number of wavelengths emitted by these systems makes it possible to investigate their structures in detail, including the electron configurations of ground and various excited states. Spectroscopy also provides a precise analytical method for finding the constituents in material having unknown chemical composition. In a typical spectroscopic analysis, a concentration of a few parts per million of a trace element in a material can be detected through its emission spectrum. In astronomy the study of the spectral emission lines of distant galaxies led to the discovery that the universe is expanding rapidly and isotropically independent of direction. The finding was based on the observation of a Doppler shift of spectral lines.