Ordered arrays of colloidal submicrometer-sized silica particles deposited onto silicon wafers were irradiated with MeV Si ions. The spherical silica particles turned into oblate particles as a result of the increase ...Ordered arrays of colloidal submicrometer-sized silica particles deposited onto silicon wafers were irradiated with MeV Si ions. The spherical silica particles turned into oblate particles as a result of the increase of the particle dimension perpendicular to the ion beam direction and the decrease in the parallel direction. Pulsed laser photoacoustic spectroscopy was used to study the structural changes of the silica particles after the ion-induced shape deformation. Our purpose is to correlate the mechanical vibrations generated by the pulsed laser as a function of the Si irradiation parameters: ion energy and fluence. Fast Fourier transform analysis of the photoacoustic signal was carried out in order to obtain the normal vibration modes of the system. The size, size distribution and shape of the silica particles were determined by scanning electron microscopy. Our results revealed significant structural differences between the spherical and the deformed silica particles.展开更多
A new method for measurement of the nonlinearity parameter B / A of liq uids by means of photoacoustic pulses is dcscribed. The photoacoustic pulsc is gener ated by a focused laser pulse via the laser-induced breakdow...A new method for measurement of the nonlinearity parameter B / A of liq uids by means of photoacoustic pulses is dcscribed. The photoacoustic pulsc is gener ated by a focused laser pulse via the laser-induced breakdown mechanism in liquids.Inthe range pf the propagation distance, in which the photoacoustic pulses were meas ured, the variation of the amplitude of photoacoustic pulse with the distance is very close to the spherical attenuation law. From the variation of the rise time of photoacoustic pulse wavefront propagating through a certain distance, the parameter B / A of liquid is determined. Comparing with the plane pulsed wave with bounded beam, the effect of diffraction may e avoided by using the spherical pulsed wave. The nonlinearity parameter B / A of water is obtained by the present method. the results are rcasonably good.展开更多
基金supported by DGAPA-UNAM projects IN-101210,IN-117208CONACYT grants No.128274,123143 and 82919the ICyTDF for the financial support
文摘Ordered arrays of colloidal submicrometer-sized silica particles deposited onto silicon wafers were irradiated with MeV Si ions. The spherical silica particles turned into oblate particles as a result of the increase of the particle dimension perpendicular to the ion beam direction and the decrease in the parallel direction. Pulsed laser photoacoustic spectroscopy was used to study the structural changes of the silica particles after the ion-induced shape deformation. Our purpose is to correlate the mechanical vibrations generated by the pulsed laser as a function of the Si irradiation parameters: ion energy and fluence. Fast Fourier transform analysis of the photoacoustic signal was carried out in order to obtain the normal vibration modes of the system. The size, size distribution and shape of the silica particles were determined by scanning electron microscopy. Our results revealed significant structural differences between the spherical and the deformed silica particles.
文摘A new method for measurement of the nonlinearity parameter B / A of liq uids by means of photoacoustic pulses is dcscribed. The photoacoustic pulsc is gener ated by a focused laser pulse via the laser-induced breakdown mechanism in liquids.Inthe range pf the propagation distance, in which the photoacoustic pulses were meas ured, the variation of the amplitude of photoacoustic pulse with the distance is very close to the spherical attenuation law. From the variation of the rise time of photoacoustic pulse wavefront propagating through a certain distance, the parameter B / A of liquid is determined. Comparing with the plane pulsed wave with bounded beam, the effect of diffraction may e avoided by using the spherical pulsed wave. The nonlinearity parameter B / A of water is obtained by the present method. the results are rcasonably good.
