Context :

Aims : The aims of our study are to improve the orbital elements of the giant , and to derive the spectroscopic orbit for the white dwarf companion .
Spectral variations related to the 2006 outburst are also studied .

Methods : We performed an analysis of about seventy optical and near infrared spectra of RS Oph that were acquired between 1998 and June 2008 .
The spectroscopic orbits have been obtained by measuring the radial velocities of the cool component absorption lines and the broad H \alpha emission wings , which seem to be associated with the hot component .
A set of cF-type absorption lines were also analyzed for a possible connection with the hot component motion .

Results : A new period of 453.6 days , and a mass ratio , q = M _ { g } / M _ { h } = 0.59 \pm 0.05 , were determined .
Assuming a massive white dwarf as the hot component ( M _ { h } = 1.2 - 1.4 M _ { \odot } ) the red giant mass is M _ { g } = 0.68 - 0.80 M _ { \odot } and the orbit inclination , i = 49 ^ { \circ } -52 ^ { \circ } .
The cF-type lines are not associated with either binary component , and are most likely formed in the material streaming towards the hot component .
We also confirm the presence of the Li I doublet in RS Oph and its radial velocities fit very well the M-giant radial velocity curve .
Regardless of the mechanism involved to produce lithium , its origin is most likely from within the cool giant rather than material captured by the giant at the time of the nova explosion .

The quiescent spectra reveal a correlation of the H I and He I emission line fluxes with the monochromatic magnitudes at 4800 Å indicating that the hot component activity is responsible for those flux variations .
We also discuss the spectral characteristics around 54–55 and 240 days after the 2006 outburst .
In April 2006 most of the emission lines present a broad pedestal with a strong and narrow component at about -20 km s ^ { -1 } and two other extended emission components at -200 and +150 km s ^ { -1 } .
These components could originate in a bipolar gas outflow supporting the model of a bipolar shock-heated shell expanding through the cool component wind perpendicularly to the binary orbital plane .
Our observations also indicate that the cF absorption system was disrupted during the outburst , and restored about 240 days after the outburst , which is consistent with the resumption of accretion .

Conclusions :