Problems and Solutions on Thermodynamics and Statistical Mechanics

Statistical Phy~ic~ 383

Atomic weight of sodium = 23.

(CUSPEA)

(a) We take observations along the z-direction. The Maxwell-

Solution:

Boltzmann distribution for v, is given by

The Doppler shift of frequency is given by

Thus

and

(b) The magnitude of the Doppler broadening is

40 x 10-3 3 x 108

= 1.04 X X 58961( = 6.13 x 10-31( ,

(c) The broadening due to collisions is

1

AUM -,

7

where r is the mean free time between two successive collisions (of a Na

atom). We have r = b, where v is the average velocity of Na atom and A