Selective reflection of light from dense sodium vapors

The resonant collisional broadening of the D-1 and D-2 lines of sodium atom s was studied by the method of selective reflection of light for vapor pres sures up to 5 x 10(18) cm(-3). As the collisional line broadening becomes c omparable to the fine splitting, the spectrum of selective reflection exhib its the interrelation between the contributions of the D-1 and D-2 lines wi th a continuous change from the doublet structure to the singlet one. The e xperimental data were found to be in good agreement with calculations based on the model of binary collisions.