Electron-antineutrino spectrum from precision measurements of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mrow> <mml:mmultiscripts> <mml:mrow> <mml:mi>Pr</mml:mi> </mml:mrow> <mml:mprescripts/> <mml:none/> <mml:mn>

The $^{144}\mathrm{Ce}--^{144}\mathrm{Pr}$ electron antineutrino source is one of the most suitable radiochemical sources for experiments searching for the oscillations of active neutrinos to the light sterile state. In the current work the $\ensuremath{\beta}$ spectra of the $^{144}\mathrm{Ce}--^{144}\mathrm{Pr}$ source have been measured by two types of $\ensuremath{\beta}$ spectrometers based on silicon Si(Li) detectors in order to determine the energy spectrum of electron antineutrinos emitted in the $\ensuremath{\beta}$ decay of $^{144}\mathrm{Pr}$ nuclei. The nuclear shape factor of the ground state beta transition in $^{144}\mathrm{Pr}\ensuremath{-}^{144}\mathrm{Nd}$ has been obtained with high precision: $C(W)=1+(\ensuremath{-}0.0301\ifmmode\pm\else\textpm\fi{}0.0007)W+(\ensuremath{-}0.101\ifmmode\pm\else\textpm\fi{}0.006){W}^{\ensuremath{-}1}$. The reduced cross section for the inverse beta decay reaction on hydrogen for the $^{144}\mathrm{Pr}$ electron antineutrino source has been defined as $(4.7344\ifmmode\pm\else\textpm\fi{}{0.0006}_{\mathrm{stat}}\ifmmode\pm\else\textpm\fi{}{0.013}_{\mathrm{syst}})\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}44}\text{ }\text{ }{\mathrm{cm}}^{2}\text{ }{\text{decay}}^{\ensuremath{-}1}$ that provides sufficient sensitivity to search for a sterile neutrino with a mass of ${m}_{4}\ensuremath{\sim}1\text{ }\text{ }\mathrm{eV}$ and a mixing angle $Si{n}^{2}(2{\ensuremath{\theta}}_{14})\ensuremath{\sim}0.005$ using the standard disappearance method.