| Lyman Series |
Article Index for Lyman |
Website Links For Lyman |
Information AboutLyman Series |
| CATEGORIES ABOUT LYMAN SERIES | |
| emission spectroscopy | |
| hydrogen physics | |
|
HISTORY The first line in the ultraviolet spectrum of the Lyman series was discovered in 1906 by Harvard physicist Theodore Lyman , who was studying the ultraviolet spectrum of electrically excited hydrogen gas. The rest of the lines of the spectrum were discovered by Lyman from 1906-1914. The spectrum of radiation emitted by hydrogen is non-continuous. Here is an illustration of the first series of hydrogen emission lines: Historically, explaining the nature of the hydrogen spectrum was a considerable problem in Physics . Nobody could predict the Wavelength s of the hydrogen lines until 1885 when the Balmer Formula gave an empirical formula for the visible hydrogen spectrum. Within five years Johannes Rydberg came up with an Empirical Formula that solved the problem, presented first in 1888 and in final form in 1890. Rydberg managed to find a formula to match the known Balmer Series emission lines, and also predict those which were not yet discovered. Different versions of the Rydberg formula with different simple numbers were found to generate different series of lines. THE LYMAN SERIES The version of the Rydberg Formula which generated the Lyman series was: : Where ''n'' is a natural number greater or equal than 2 (i.e. ''n'' = 2,3,4,...). Therefore, the lines seen in the image are the wavelengths corresponding to n=2 on the left, to n= on the right (there are infinitely many spectral lines, but they become very dense as they approach to ''n''=, so only some of the first lines and the last one appear). The wavelengths (nm) in the Lyman series are all ultraviolet: EXPLANATION AND DERIVATION In 1913, when Niels Bohr produced his Bohr Model theory, the reason why hydrogen spectral lines fit Rydberg's formula was explained. Bohr found that the electron bound to the hydrogen atom must have quantized energy levels described by the following formula: : According to Bohr's third assumption, whenever an electron falls from an initial energy level() to a final energy level(), the atom must emit radiation with a wavelength of: : There is also a more comfortable notation when dealing with energy in units of Electronvolt s and wavelengths in units of Angstrom s: : Replacing the energy in the above formula with the expression for the energy in the hydrogen atom where the initial energy corresponds to energy level ''n'' and the final energy corresponds to energy level ''m'':
|