Dynamic Jahn-Teller effects in isolated C60- studied by near-infrared spectroscopy in a storage ring.

We have measured the near-infrared absorption spectrum for isolated C60- ions at room temperature. Two bands, at 9145 cm(-1) and 10460 cm(-1), have been identified in addition to the main absorption band at 9382 cm(-1), seen also at low temperature in a matrix. An interpretation based on the theory of dynamic Jahn-Teller effects is proposed.

Photodestruction of adenosine 5'-monophosphate (AMP) nucleotide ions in vacuo: statistical versus nonstatistical processes.

The lifetimes of both deprotonated adenosine 5(')-monophosphate (AMP) and protonated AMP, after 266-nm photon absorption and intramolecular vibrational redistribution, were determined to be 16 micros based on a newly developed heavy-ion storage ring technique. Protonation of the adenine nucleobase seriously affects the fragmentation mechanism: the major part of the photoexcited anions fragment in a statistical (ergodic) process, whereas nearly all the cations (>99%) fragment in a nonergodic process. In solution at natural pH the AMP anion is prevalent and photoproduct formation is therefore less important as the time for vibrational cooling is of the order of picoseconds.

Vibrationally resolved photoabsorption spectroscopy of red fluorescent protein chromophore anions.

Photoabsorption studies of red fluorescent protein chromophore anions have been performed at the ELISA electrostatic heavy-ion storage ring. The broad absorption band due to electronic excitation of the chromophores is tuned to a longer wavelength (redshifted) by extending the electronic conjugation of the molecule. A clear vibrational progression is resolved with E(vib) approximately 380 and 520 cm(-1) for two different forms of the chromophore. The vibrational modes correspond to collective motions of the entire molecular structure. It is argued that the excited electronic state has an equilibrium configuration far from that of the electronic ground state, i.e., poor Franck Condon overlap.

Absorption spectrum of the green fluorescent protein chromophore anion in vacuo.

A sensitive photoabsorption technique for studies of gas-phase biomolecules has been used at the ELISA electrostatic heavy-ion storage ring. We show that the anion form of the chromophore of the green fluorescent protein in vacuo has an absorption maximum at 479 nm, which coincides with one of the two absorption peaks of the protein. Its absorption characteristics are therefore ascribed to intrinsic chemical properties of the chromophore. Evidently, the special beta-can structure of the protein provides shielding of the chromophore from the surroundings without significantly changing the electronic structure of the chromophore through interactions with amino acid side chains.

Observation of a 1/t decay law for hot clusters and molecules in a storage ring.

The exponential law is valid both for decay from a single quantum state into a continuum and for an ensemble maintained in thermal equilibrium. For statistical decay of an ensemble of isolated systems with a broad energy distribution, the exponential decay is replaced by a 1/t distribution. We present confirmation of this decay law by experiments with cluster anions in a small electrostatic storage ring. Deviations from the 1/t law for such an ensemble give important information on the dynamics of the systems. As examples, we present measurements revealing strong radiative cooling of anions of both metal clusters and fullerenes.

Dissociation energy for C(2) loss from fullerene cations in a storage ring.

We have stored positively charged fullerene ions C(+)(n) (n even, from 48 to 70 and 76), C(2+)(60) and C(2+)(70) in an electrostatic storage ring and have measured the rate of emission of neutral fragments as a function of time. In the time range of the measurements, 50 micros to a few milliseconds, the rate decreases strongly due to radiative cooling of the molecules. Using the cooling rate predicted from a dielectric model, we have extracted the dissociation energies for C(2) loss from the measurements. As expected, the energies are largest for the "magic" fullerenes, C(50), C(60), and C(70), and the value of 9.8+/-0.1 eV for C(2) loss from C(+)(60) is in reasonable agreement with theory and with other recent experiments.

High-resolution vacuum-ultraviolet spectroscopy of an electron-cooled D- beam.

The shape parameters for the lowest-lying (1)P(o) resonance, (2)¿0¿-3, of D- have been measured using high-resolution vacuum-ultraviolet spectroscopy. The experiment was performed at the storage ring ASTRID, and the resonance was resolved by applying electron cooling to reduce the velocity spread of the ion beam. The resonance has a width of 37(3) microeV while the asymmetry parameter q of the Fano profile is -16(3). These values present the first critical test of a large number of theoretical calculations.