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Energy resolved photodissociation studies of CO3-·(H2O)n, n=1,2,3 are reported for photon energies ranging from 1.95 to 2.2 eV. The only dissociation channel observed is the loss of all attached water molecules to give unclustered CO3- as the sole photofragment ion. The cross section for this mechanism is substantially higher than that for the bare ion, and the sharp structure observed in the spectrum of the bare ion is nearly lost in the clusters. Analysis of the kinetic energy distributions for the photofragment ions places an upper limit of 20 μs on the lifetime of the excited clusters, and demonstrates that approximately 95% of the excess energy in the cluster remains in the CO3- containing fragment rather than being partitioned into relative translation of the photofragments or into internal motion of the water fragments. The dissociation mechanism begins with a bound–bound 2A1←2B1 transition within the core CO3- ion. Internal conversion returns the core ion to the electronic ground state with substantial vibrational excitation; redistribution of this vibrational energy results in vibrational predissociation of the cluster. The relations of this mechanism to those that occur in the bare ion and to other vibrational predissociation experiments on clusters are discussed. [ABSTRACT FROM AUTHOR]

The dynamics of CO3- photodissociation is studied with a new photodissociation spectrometer that allows kinetic energy-resolved detection of parent ions and photofragments. Kinetic energy release distributions, photodissociation spectra, and the dependence of the photofragment intensity on the laser power and background pressure are presented. Photodissociation of CO3- in the energy range 1.95–2.2 eV leads to CO2+O- fragments, and is found to occur by two distinct mechanisms. These mechanisms involve three electronic states that correlate with CO2+O-—the 2B1 ground state, a 2A1 weakly bound state, and a repulsive 2B2 state. The first mechanism begins with a low cross section 2A1 ← 2B1 transition that gives structure to the spectra. From this intermediate state, a second photon carries the ion to the 2B2 state. Dissociation to the observed photofragments occurs rapidly on the repulsive surface. In this two photon mechanism, at least 20% of the available energy is disposed of in relative translation of photofragments. The second mechanism is also initiated by the 2A1 ← 2B1 transition. Deexcitation of the 2A1 bound state by internal conversion, however, leads to high lying vibrational levels of the ground 2B1 state. These vibrational levels are found to have an enhanced collision-induced dissociation cross section. [ABSTRACT FROM AUTHOR]

On-orbit firings of both liquid and solid rocket motors provide localized disturbances to the plasma in the upper atmosphere. Large amounts of energy are deposited to ionosphere in the form of expanding exhaust vapors which change the composition and flow velocity. Charge exchange between the neutral exhaust molecules and the background ions (mainly \O^+) yields energetic ion beams. The rapidly moving pickup ions excite plasma instabilities and yield optical emissions after dissociative recombination with ambient electrons. Line-of-sight techniques for remote measurements rocket burn effects include direct observation of plume optical emissions with ground and satellite cameras, and plume scatter with UHF and higher frequency radars. Long range detection with HF radars is possible if the burns occur in the dense part of the ionosphere. The exhaust vapors initiate plasma turbulence in the ionosphere that can scatter HF radar waves launched from ground transmitters. Solid rocket motors provide particulates that become charged in the ionosphere and may excite dusty plasma instabilities. Hypersonic exhaust flow impacting the ionospheric plasma launches a low-frequency, electromagnetic pulse that is detectable using satellites with electric field booms. If the exhaust cloud itself passes over a satellite, in situ detectors measure increased ion-acoustic wave turbulence, enhanced neutral and plasma densities, elevated ion temperatures, and magnetic field perturbations. All of these techniques can be used for long range observations of plumes in the ionosphere. To demonstrate such long range measurements, several experiments were conducted by the Naval Research Laboratory including the Charged Aerosol Release Experiment, the Shuttle Ionospheric Modification with Pulsed Localized Exhaust experiments, and the Shuttle Exhaust Ionospheric Turbulence Experiments. [ABSTRACT FROM PUBLISHER]

Unexpectedly high concentrations of ultrafine particles were observed over a wide range of latitudes in the upper troposphere and lower stratosphere. Particle number concentrations and size distributions simulated by a numerical model of ion-induced nucleation, constrained by measured thermodynamic data and observed atmospheric key species, were consistent with the observations. These findings indicate that, at typical upper troposphere and lower stratosphere conditions, particles are formed by this nucleation process and grow to measurable sizes with sufficient sun exposure and low preexisting aerosol surface area. Ion-induced nucleation is thus a globally important source of aerosol particles, potentially affecting cloud formation and radiative transfer. [ABSTRACT FROM AUTHOR]