  The theoretical assertion that the Fano asymmetry parameter and the
asymptotic initial phase of a harmonic oscillator interacting with a continuum
are interrelated is experimentally verified. By an example of coherent fully
symmetric A1g phonons in bismuth that are excited by ultrashort laser pulses at
liquid helium temperature, it is demonstrated that, for negative values of the
asymmetry parameter, the asymptotic phase increases as the modulus of the
parameter decreases.
