[en] The excitation function of the reaction ²³¹Pa(n,f) was measured from 130 to 450 keV with a neutron energy resolution of 5 keV. The measurements confirmed the existence of the two structures already observed around Esub(n)=200 keV and Esub(n)=330 keV and revealed a narrow resonance around Esub(n)=160 keV. The use of an energy resolution of only 2 keV showed that the width of this resonance is <=2 keV. The angular distributions of the fission fragments were also measured in the vicinity of these three structures with an energy resolution of 5 keV. The excitation function and the angular distributions were reproduced simultaneously with the aid of a statistical model allowing for the competition between the different exit channels (neutron emission, gamma emission, fission through a barrier with two peaks). This analysis shows that the narrow resonance at 160 keV has all the characteristics of a pure vibrational resonance (KJsup(π))=(33⁺). The resonances at 200 keV and 330 keV are interpreted as corresponding to the vibrational states Ksup(π)=0⁺ and Ksup(π)=0^-. (author)