Using both Rayleigh scattering and time-resolved emission spectroscopy, we have recorded the spatial and temporal evolution of laser-generated sparks in argon from changes during the first tens of nanoseconds to complete dissipation, which occurs in a time span of approximately 5 ms. Maps of either emission intensity or argon density spanning the entire region affected by the energy deposited by the laser show the dissipation of the spark in detail. Immediately after ignition, the argon plasma occupies an ellipsoidal volume of roughly 3-mm vertical (axial) length. After approximately 20–40 μs, the spark region has transformed into a toroidal shape in a plane perpendicular to the vertical axis, with a radius of approximately 1.5 mm. The torus rises slowly up and expands noticeably in the radial direction. A record of peak temperatures of the spark ranging from approximately 10,000 K at 60-μs delay time to approximately 450 K at 4-ms delay time indicate cooling rates from approximately 100 to 1 K/μs at these times.
© 2003 Optical Society of America
(020.0020) Atomic and molecular physics : Atomic and molecular physics
(290.5870) Scattering : Scattering, Rayleigh
(300.2140) Spectroscopy : Emission
(300.6500) Spectroscopy : Spectroscopy, time-resolved
(350.5400) Other areas of optics : Plasmas
Marc Longenecker, Lutz Hüwel, Lou Cadwell, and Deborah Nassif, "Laser-generated spark morphology and temperature records from emission and Rayleigh scattering studies," Appl. Opt. 42, 990-996 (2003)