Speaker
Description
Fullerenes, in both neutral and ionized forms, are the largest molecular species identified in the interstellar medium. Among their many derivatives, ionized species—including protonated, oxidized, and other exohedral variants— have attracted considerable astrophysical interest. Recent advances in synthesis methods have enabled the encapsulation of small molecules within fullerene cages, making the spectroscopic investigation of ionized endohedral fullerenes possible.
We present the gas-phase experimental vibrational spectra of H2O@C60 in its protonated and radical cationic forms. The spectra of the ionized endohedral fullerenes are compared to the vibrational spectra of C60H+ and C60+. We found that the vibrational spectra of the ionized fullerenes are almost entirely identical to their endohedral versions. The phenomenon is likely due to a shielding effect, where the polarization of the fullerene cage reduces the dipole moment of the whole system, thereby suppressing the IR intensities associated with the vibrational modes of the encapsulated water molecule.
Consequently, ionized endohedral fullerenes have the same astrophysical signatures as the ionized fullerenes they derive from, making them potentially indistinguishable in spectra detected from the interstellar medium.
