The non-Lorentzian wings of alkali resonance lines: the determination of the atom number density in pure and mixed alkali vapours

The improved method for the determination of the atom number densities in pure and mixed alkali vapours has been proposed. In order to obtain the correct results one has to go beyond the simple Lorentzian shape of the quasistatic absorption profile. The method has been tested by the white-light absorption measurements in the pure K, Rb and Cs vapours. The statistical accuracy of the obtained data for the atom number density is +or-3%. The method has been applied for determining the atom number densities in the vapour over the Rb-Cs mixture. The obtained values have been used in the evaluation of the effective C_6 constants for Rb*-Cs interaction: C6eff=(4.9+or-0.3)* 10-30 cm^6 s^-1 for the D2 line. The theory predicts C6eff=4.95*10-30 cm^6 s^-1 for the D1 line and C6eff=2.37*10-30 cm^6 s(-1) for the D2 line.