  Long-slit observations of the blue compact galaxy Haro 2 have been performed
to detect the Halpha emission originating in the partially ionized wind
outflowing at 200 km/s, that had been previously detected with the Hubble Space
Telescope. A shallow broadening of the Halpha line wings has been observed,
consistent with the existence of an expanding shell. The rotation curve shows
two dips at the same systemic velocity as the nucleus. At the positions of the
dips the Halpha line is clearly broadened with respect to the central core.
This broadening is produced by the outer layers of the expanding shell. From
the position of these dips we estimate the size of the shell to be around 20''
in diameter, with a corresponding kinematical age between 5 and 6 Myr. A
comparison of the Halpha and Ly_alpha profiles shows that Ly_alpha is
significantly broader than Halpha, with an additional emission in the red wing.
We interpret this redshifted source of Ly_alpha emission as line photons
backscattered by the receding part of the expanding shell. These observations
outline the extremely high sensitivity of the Ly_alpha line to the structure
and kinematics of the interstellar medium.
