SYMPATHETIC COOLING OF TRAPPED NEGATIVE-IONS BY SELF-COOLED ELECTRONSIN A FOURIER-TRANSFORM ION-CYCLOTRON RESONANCE MASS-SPECTROMETER

Hot electrons confined in a Penning trap at 3 tesla self-cool to near room temperature in a few seconds by emission of cyclotron radiation. Here, we show that such cold electrons can ''sympathetically'' cool, i n similar to 10 s, laser desorbed/ionized translationally hot Au- or C -70(-) ions confined simultaneously in the same Penning trap. Unlike ' 'buffer gas'' cooling by collisions between ions and neutral gas molec ules, sympathetic cooling by electrons is mediated by the mutual long- range Coulomb interaction between electrons and ions, so that translat ionally hot ions can be tooled without internal excitation and fragmen tation. It is proposed that electrosprayed multiply charged macromolec ular ions can be cooled sympathetically, in the absence of ion-neutral collisions, by self-cooled electrons in a Penning trap. (C) 1997 Amer ican Society for Mass Spectrometry.