Time-resolved studies of the interactions between pulsed lasers and aerosols

Abstract

Studies of the interaction between a pulsed CO2 laser and micrometer-sized aqueous and organic particles by use of light-scattering methods and step-scan Fourier-transform infrared (FTIR) spectroscopy are reported. Visible two-color extinction experiments indicate primary particle shattering, accompanied by a high fraction of vaporization, followed by secondary particle evaporation. The extent of the latter depends on the pulse intensity and particle composition. Angle-resolved light-scattering investigations provide insight into the aerosol size distribution and temperature following the pulsed heating event. The time dependence of the vapor plume, monitored with step-scan FTIR spectroscopy, confirms that a large fraction of the initial particle is quickly evaporated during the shattering event, followed by secondary fragment evaporation and thermal expansion.

Finite Element Analysis Modeling of Pulse-Laser Excited Photothermal Deflection (Mirage Effect) from Aerosols

“…Previous reports on aerosols have focused on the associated heat and mass transfer processes that occur regarding their influence on the atmosphere when aerosols are heated with a source of light such as lasers. [19][20][21][22] Heating an aerosol with a laser beam induces temperature gradients in the fluid surrounding the particle, causing a change in the index of refraction of the fluid in the vicinity of the particle. The amount of energy an aerosol absorbs from the incident light beam depends on the complex index of refraction of the particle as well as on its optical size (where the optical size x is given by x ¼ 2pr/k, where r and k are the particle radius and laser wavelength, respectively).…”

Modeling of vapor-droplet plumes ablated from multiple spots

“…The diameter D p = 2 mm of the mixture particles is assumed to comply with the measurements [10], where the emission of fine droplets with the size of 2 mm is observed during the interaction of short laser pulses with water or soft biological tissues. The experimental study of aerosol with micron-size water droplets [17] has shown that the droplet diameter decrease of 10% occurs only after $20 ms even in case of higher energy laser pulses. Since the particle diameter is assumed unaltered in-flight, the extinction factor Q ext (l) and K ext (l) are constant over the simulation time.…”

Spectroscopy and energetics of the acetylene molecule: dynamical complexity alongside structural simplicity

“…C 2 H 2 or C 2 HD scattered off LiF surfaces [35,40]). The diffusion-cell experiments on aerosols also paved the way for Miller to establish an extensive collaboration on time-of-flight mass spectrometry of laserirradiated aerosols with Tomas Baer and coworkers [222][223][224][225][226][227][228][229][230][231][232][233][234].…”