Potential-barrier effects in photoabsorption. III. Application to 4d-shell photoabsorption in lanthanum

An exploratory calculation of the photoabsorption cross section near the $4d$ ionization threshold of lanthanum metal is carried out. The level structure of the configuration $4{d}^{9}4f$ is found to be altered by interaction with the continuum configuration 4d⁹ε f. The Fano profile of the resonance above threshold is calculated, as are the oscillator strengths of the discrete states below threshold. Our results provide the ground work for more detailed calculations.