NASA ABSTRACT
Characterizing the nature of the dusty plasma in the pulsed discharge nozzle (PDN) environment of NASA-AMES' interstellar simulation chamber through laboratory simulations and experimental data. Astrophysical implications.
Jerome Remy, TU/e Eindhoven, Applied Physics Dpt, Eindhoven, The Netherlands-EU
Ludovic Biennier, Farid Salama, NASA AMES research center, Space Science Division, Moffett Field, USA
Interstellar dust presents a continuous size distribution from large molecules, radicals and ions to nanometer-sized particles to micron-sized grains. The lower end of the dust size distribution is thought to be responsible for the discrete spectral features seen in emission in the IR (UIBs) and in absorption in the visible (DIBs). The higher end of the distribution is thought to be responsible for the continuum emission plateau seen in the IR and for the strong absorption seen in the interstellar UV extinction curve. Although dust with all its components plays an important role in the evolution of interstellar chemistry, little is know on its formation and destruction processes. Recent space observations in the UV (HST) and in the IR (ISO) help place size constraints on the molecular component of carbonaceous IS dust and indicate that small (i.e., subnanometer) PAHs cannot contribute significantly to the IS features in the UV and in the IR. Laboratory studies of large molecular and nano-sized IS dust analogs formed from PAH precursors have been performed in our laboratory under conditions that simulate diffuse ISM environments (the particles are cold (100 K vibrational energy), isolated in the gas phase and exposed to a high--energy discharge environment). These studies use a pulsed discharge nozzle (PDN) source coupled to a cavity ringdown spectrometer (CRDS) for high sensitivity detection. Attempts have been made to characterize the nature of the dusty plasma that is generated in the free jet expansion. The poster will describe the approach that was followed in order to provide a representation of the nature of the plasma generated in the experiments. The poster will discuss the results derived from the experimental and theoretical study of the electron density and temperature of the dusty plasma providing an insight into the nature of the processes that occur in the plasma. This information is used to derive information on the nature (size) of interstellar dust particles and IS dust growth and destruction processes.
* Reference: J. Remy, L. Biennier and F. Salama, Plasma Sources science and technology, IoP, August 2003, pp. 295-301
