Stationary States The Bohr Frequency Principle

These facts and some observation about the frequencies of spectral lines were the inspiration for Bohr s two postulates, which may be expressed in the following way  

The existence of stationary states. An atomic system can exist in certain stationary states, each one corresponding to a definite value of the energy W of the system, and transition from one state to another is accompanied by the emission or absorption as radiation, or the transfer to or from another system of atoms or molecules, of an amount of energy equal to the energy difference of the two states. 

The Bohr frequency rule. The frequency of the radiation absorbed by a system and associaled with the transition from an initial stale with energy W to a final stale with energy W% is 

The two postulates are compatible with the observation that the frequencies of the spectral lines emitted by an atom can be represented as the differences between pairs of a set of frequency values, called the term values or spectral terms of the atom. These term values are now seen to be the values of the energy of the stationary states divided by h (to give frequency, in sec- 1), or by he (to give wave number, in cm- 1, as is customarily given in tables of term values). 

In this equation jBh is called the Rydberg constant for hydrogen the value for the Rydberg constant for hydrogen is 109,677.76 cm 1. The letter h is Planck s constant, and c the velocity of light. The letter n is the toted quantum number it may have integral values 1,2, 3, 4,  

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