To establish safety parameters, we in vitro studied the increase in intrapulpal temperature caused by the use of a cw CO2 laser. A thermistor was implanted in the inner part of the pulpal chamber of 25 human lower third molars to measure the intrapulpal temperature produced by laser powers between 2-10 W and exposure times of 0.5-25.0 s. The Pearson linear correlation factor applied to the measured values showed there is a direct relationship between the independent variable and the applied power. A variance analysis produced the linear regression equation: T = 1.10 + (0.127)E where T is the temperature and E the energy. The results showed that, with a power of 4 W and maximum exposure time of 2:5 s (10 J) and a power density of 12,738.85 W cm-2, there will be no damaging reactions affecting the pulpal tissues.

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This article presents the use of piezoelectric PVDF films as a sensor for the vapor stream in laser ablation experiments. The analysis of the PVDF electric signal gives the translational temperature and the vapor drift velocity of the ablated plume. A PVDF sensor was used in a tungsten ablation experiment, using HyBrID copper laser, and it was obtained a translational temperature of 9×104 K and a drift velocity of 4×105 cm/s.

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The observation of current in the afterglow of the discharge in a pulsed hollow-cathode lamp illuminated by tunable lasers, combined with optogalvanic techniques, provides a simple and reliable tool for multi-step photoionization spectroscopy studies. A three-photon photoionization spectroscopy study was performed in a uranium hollow-cathode lamp, using this combination of techniques. Single-, double-and triple-frequency photoionization paths were identified for uranium, in the range between 5900 and 6060 Å.

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Uranium photoionization was observed in the afterglow of pulsed hollow cathode lamps illuminated by a dye laser tuned near the electronic transition around 591.5 nm ͑ 5 L 6 0 Ϫ16 900 cm Ϫ1 7 M 7 ͒. The photoionization signal was used to monitor the time evolution of the ground state uranium vapor density in the cathode hole. Lifetimes over 1 ms were measured for the uranium vapor; that makes this device attractive for multistep photoionization spectroscopy. The obtained results lead to the conclusion that these long times are due to cluster formation in the afterglow.

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