Context : The paper analyzes the structure and dynamics of a quiescent prominence that occurred on October 22 , 2013 and was observed by several instruments including the Interface Region Imaging Spectrograph ( IRIS ) .

Aims : We aim to determine the physical characteristics of the observed prominence using Mg ii k and h ( 2796 and 2803 Å ) , C ii ( 1334 and 1336 Å ) , and Si iv ( 1394 Å ) lines observed by IRIS .
In addition we study the dynamical behavior of the prominence .

Methods : We employed the one-dimensional non-LTE ( departures from the local thermodynamic equilibrium – LTE ) modeling of Mg ii lines assuming static isothermal-isobaric slabs .
We selected a large grid of models with realistic input parameters expected for quiescent prominences ( temperature , gas pressure , effective thickness , microturbulent velocity , height above the solar surface ) and computed synthetic Mg ii lines .
The method of Scargle periodograms was used to detect possible prominence oscillations .

Results : We analyzed 2160 points of the observed prominence in five different sections along the slit averaged over ten pixels due to low signal to noise ratio in the C ii and Si iv lines .
We computed the integrated intensity for all studied lines , while the central intensity and reversal ratio was determined only for both Mg ii and C ii 1334 lines .
We plotted several correlations : time evolution of the integrated intensities and central intensities , scatter plots between all combinations of line integrated intensities , and reversal ratio as a function of integrated intensity .
We also compared Mg ii observations with the models .
Results show that more than two-thirds of Mg ii profiles and about one-half of C ii 1334 profiles are reversed .
Profiles of Si iv are generally unreversed .
The Mg ii and C ii lines are optically thick , while the Si iv line is optically thin .

Conclusions : The studied prominence shows no global oscillations in the Mg ii and C ii lines .
Therefore , the observed time variations are caused by random motions of fine structures with velocities up to 10 km s ^ { -1 } .
The observed average ratio of Mg ii k to Mg ii h line intensities can be used to determine the prominence ’ s characteristic temperature .
Certain disagreements between observed and synthetic line intensities of Mg ii lines point to the necessity of using more complex two-dimensional multi-thread modeling in the future .