Spectroscopic investigation of laser-initiated low-pressure plasmas in atmospheric gases.
Laser-initiated breakdown of N2, O2, and Ar has been investigated at sub-atmospheric pressures using a pulsed (10-nsec) Nd:yttrium aluminum garnet (Nd:YAG) laser at 1.06 μm. Breakdown thresholds have been determined from 3 to 760 Torr, and spectral analysis of the plasma emission has been carried out at 10 and 125 Torr over the 300–600-nm range. Sharp spectral features arising from highly excited singly and multiply charged ions are reported as well as an underlying continuum at intermediate pressure. Time-resolved measurements indicate a complex kinetic dynamic optical behavior.
Sampling statistics and considerations for single-shot analysis using laser-induced breakdown spectroscopy
Abstract A statistical analysis of single-shot spectral data is reported for laser-induced breakdown spectroscopy (LIBS). Fluctuations in both atomic emission and plasma continuum emission are investigated in concert for a homogenous gaseous flow, and fluctuations in plasma temperature are reported based on iron atomic emission in an aerosol-seeded flow. Threshold irradiance for plasma initiation and plasma absorption were investigated for pure gaseous and aerosol streams, with detailed statistical measurements performed as a function of pulse energy in the breakdown regime. The ratio of the analyte atomic emission intensity to the continuum emission intensity (peak/base) provided a robust signal for single-shot LIBS analysis. Moreover, at optimal temporal delay, the precision of the LIBS signal was maximized for pulse energies within the saturation regime with respect to plasma absorption of incident energy. Finally, single-shot temperature measurements were analyzed, leading to the conclusion that spatial variations in the plasma volume formation and subsequent plasma emission collection, play important roles in the overall shot-to-shot precision of the LIBS technique for gaseous and aerosol analysis.
The lights that failed: European international history, 1919-1933
PART I: THE RECONSTRUCTION OF EUROPE, 1918-1929 1. The Hall of Mirrors: Peacemaking in the West 2. Distant Frontiers: Peacemaking in the East 3. Revolution from the Left: The Soviet Union and the Post-War Settlement 4. The Primacy of Economics: Reconstruction in Western Europe, 1919-1924 5. The Primacy of Nationalism: Reconstruction in Eastern and Central Europe 6. Revolution from the Right: Italy, 1919-25 7. The Geneva Dream: The League of Nations and Post-War Internationalism 8. New Dawn? Stabilisation in Western Europe after Locarno 9. Faltering Reconstruction: Cracks in the Locarno Facade 10. Troubled Waters: Uncertainties in Italy, Eastern Europe and the Soviet Union 11. Faltering Internationalism: Disarmament and Security after Locarno Conclusion: Europe Reconstructed? PART II: THE HINGE YEARS, 1930-1933 12. The Diplomacy of the Depression: Economics and Foreign Policy 13. Beyond Europe: The Manchurian Crisis 14. The Poisoned Chalice: The Pursuit of Disarmament Conclusion: The Hinge Years Appendices Select Bibliography