  Aims. We report on ESPRESSO high-resolution transmission spectroscopic
observations of two primary transits of the highly-irradiated, ultra-hot
Jupiter-size planet WASP-76b. We investigate the presence of several key atomic
and molecular features of interest that may reveal the atmospheric properties
of the planet. Methods. We extracted two transmission spectra of WASP-76b with
R approx 140,000 using a procedure that allowed us to process the full ESPRESSO
wavelength range (3800-7880 A) simultaneously. We observed that at a high
signal-to-noise ratio, the continuum of ESPRESSO spectra shows wiggles that are
likely caused by an interference pattern outside the spectrograph. To search
for the planetary features, we visually analysed the extracted transmission
spectra and cross-correlated the observations against theoretical spectra of
different atomic and molecular species. Results. The following atomic features
are detected: Li I, Na I, Mg I, Ca II, Mn I, K I, and Fe I. All are detected
with a confidence level between 9.2 sigma (Na I) and 2.8 sigma (Mg I). We did
not detect the following species: Ti I, Cr I, Ni I, TiO, VO, and ZrO. We impose
the following 1 sigma upper limits on their detectability: 60, 77, 122, 6, 8,
and 8 ppm, respectively. Conclusions. We report the detection of Li I on
WASP-76b for the first time. In addition, we found the presence of Na I and Fe
I as previously reported in the literature. We show that the procedure employed
in this work can detect features down to the level of ~ 0.1 % in the
transmission spectrum and ~ 10 ppm by means of a cross-correlation method. We
discuss the presence of neutral and singly ionised features in the atmosphere
of WASP-76b.
