HANLE EFFECT IN YB WITH A PHASE DIFFUSING LASER FIELD.

The Hanle resonances for the **1S//0-**3P//1 transition at 5556 angstrom in Yb**1**7**4 were investigated using a well-characterized phase diffusing laser field. The synthesized spectral density of the phase diffusing laser is nearly Lorentzian, with linewidths varying from 0. 5 to 4 MHz. The band shape of the synthesizing Gaussian noise is also Lorentzian, with a bandwidth of 100 MHz. Thus the correlation function describing the phase fluctuating laser has a simple exponential dependence. The intensity of the laser was varied from 10 to 0. 1 mW/cm**2. The width of the Hanle dip shows the characteristic broadening due to Rabi oscillations as well as the predicted of narrowing due to finite laser bandwidth. Numerical simulations of the overall Hanle resonance line shapes were also calculated and compared with experimental results.