A method for acquiring a spectrum (S) representative of a particle , comprising the following steps: - illuminating the particle with a light source ; - detecting, using a photodetector , light radiation emitted or scattered by said particle under the effect of the illumination and acquiring a spectrum (S)from the detected light radiation; wherein the method comprises : i) acquiring a first elementary spectrum (S 1 ) and forming an initial combined spectrum (S C,i=0 ) from the first elementary spectrum, the duration of the acquisition of the first elementary spectrum being determined to prevent any degradation of the particle; ii) acquiring a current elementary spectrum (S i ); iii) taking into account a reference spectrum (S ref ); iv) determining an acceptance criterion (C i ) of the current elementary spectrum (S i ), the acceptance criterion corresponding to a deviation between the current elementary spectrum (S i ) and the reference spectrum (S ref ); v) depending on the acceptance criterion (C i ): - accepting the current elementary spectrum (S i ) and updating the combined spectrum (S C,i ) by adding the current elementary spectrum (S i ) to the initial combined spectrum (S C,i=0 ) or to the combined spectrum resulting from a preceding iteration (S C,i-1 ); - or rejecting the current elementary spectrum; vi) reiterating ii) to vi), or exiting from the iteration; vii) determining a spectrum (S), representative of the particle , depending on the combined spectrum (Sc,i) obtained in v) of the last iteration. - illuminating the particle with a light source ; - detecting, using a photodetector , light radiation emitted or scattered by said particle under the effect of the illumination and acquiring a spectrum (S)from the detected light radiation; i) acquiring a first elementary spectrum (S 1 ) and forming an initial combined spectrum (S C,i=0 ) from the first elementary spectrum, the duration of the acquisition of the first elementary spectrum being determined to prevent any degradation of the particle; ii) acquiring a current elementary spectrum (S i ); iii) taking into account a reference spectrum (S ref ); iv) determining an acceptance criterion (C i ) of the current elementary spectrum (S i ), the acceptance criterion corresponding to a deviation between the current elementary spectrum (S i ) and the reference spectrum (S ref ); v) depending on the acceptance criterion (C i ): - accepting the current elementary spectrum (S i ) and updating the combined spectrum (S C,i ) by adding the current elementary spectrum (S i ) to the initial combined spectrum (S C,i=0 ) or to the combined spectrum resulting from a preceding iteration (S C,i-1 ); - or rejecting the current elementary spectrum; - accepting the current elementary spectrum (S i ) and updating the combined spectrum (S C,i ) by adding the current elementary spectrum (S i ) to the initial combined spectrum (S C,i=0 ) or to the combined spectrum resulting from a preceding iteration (S C,i-1 ); - or rejecting the current elementary spectrum; vi) reiterating ii) to vi), or exiting from the iteration; vii) determining a spectrum (S), representative of the particle , depending on the combined spectrum (Sc,i) obtained in v) of the last iteration. <EOS>