The luminescent quantum efficiency of Cr³⁺ ions in co-doped crystals of LiNb0<syb>3</sub> : ZnO determined by simultaneous multiple-wavelength photoacoustic and luminescence experiments

In this paper, the luminescent quantum efficiency of Cr³⁺ ions in co-doped crystals of LiNb03: ZnO: Cr³⁺ is determined by using a method based on simultaneous multiple-wavelength measurement of photoacoustic and luminescence signal after pulsed laser excitation. The quantum efficiency found in this lattice was (10 ±4)% . This result was compared with the value found from the study of the lifetime in terms of the temperature of the luminescent levels involved. In this last case, two non-equivalent crystal sites were found for Cr³⁺ ions, and two fluorescence quantum yields were determined. After the estimation of the concentration of each site by electron paramagnetic resonance experiments, the averaged fluorescence quantum yield value was (9 ± 2)% in agreement with the previous result.Facultad de Ciencias ExactasCentro de Investigaciones Óptica

The luminescent quantum efficiency of Cr³⁺ ions in co-doped crystals of LiNb0<syb>3</sub> : ZnO determined by simultaneous multiple-wavelength photoacoustic and luminescence experiments

In this paper, the luminescent quantum efficiency of Cr³⁺ ions in co-doped crystals of LiNb03: ZnO: Cr³⁺ is determined by using a method based on simultaneous multiple-wavelength measurement of photoacoustic and luminescence signal after pulsed laser excitation. The quantum efficiency found in this lattice was (10 ±4)% . This result was compared with the value found from the study of the lifetime in terms of the temperature of the luminescent levels involved. In this last case, two non-equivalent crystal sites were found for Cr³⁺ ions, and two fluorescence quantum yields were determined. After the estimation of the concentration of each site by electron paramagnetic resonance experiments, the averaged fluorescence quantum yield value was (9 ± 2)% in agreement with the previous result.Facultad de Ciencias ExactasCentro de Investigaciones Óptica

The luminescent quantum efficiency of Cr³⁺ ions in co-doped crystals of LiNb0<syb>3</sub> : ZnO determined by simultaneous multiple-wavelength photoacoustic and luminescence experiments

In this paper, the luminescent quantum efficiency of Cr³⁺ ions in co-doped crystals of LiNb03: ZnO: Cr³⁺ is determined by using a method based on simultaneous multiple-wavelength measurement of photoacoustic and luminescence signal after pulsed laser excitation. The quantum efficiency found in this lattice was (10 ±4)% . This result was compared with the value found from the study of the lifetime in terms of the temperature of the luminescent levels involved. In this last case, two non-equivalent crystal sites were found for Cr³⁺ ions, and two fluorescence quantum yields were determined. After the estimation of the concentration of each site by electron paramagnetic resonance experiments, the averaged fluorescence quantum yield value was (9 ± 2)% in agreement with the previous result.Facultad de Ciencias ExactasCentro de Investigaciones Óptica

Ground-based ultraviolet-radiation measurements during springtime in the Southern hemisphere

We report the first measurements obtained by a network of UV-B detectors established through Argentina and Chile, at locations covering latitudes extending from 53°S to 18° S. Evidence that UVB increases are detected at these latitudes during the Austral spring 1993 is presented. The destruction of the stratospheric ozone layer is generally considered one of the most serious environmental problems. It has been recently published that during October 1998 the ozone hole has been the deepest ever recorded. Reduction of the stratospheric ozone layer was un ambiguously detected about two decades ago in the Antarctic continent. Since then it has been systematically monitored by different means (satellite, balloon soundings and ground station observations. One of the most serious content reduction is the increase of biologically effective ultraviolet doses, particularly the so-called ultraviolet B radiation (280-320 nm) received at the Earth surface, with multiple possible hazards for living species. Despite these consequences, ground stations to check the UV Sun radiation are not very numerous, particularly outside the circumpolar area in the Southern Hemisphere. With the aim of studying whether the ozone depletion over the Antarctic area has extended further, and whether the possibility that UV radiation increase may begin to affect inhabited regions, a network of UVB detectors has been established through Argentina and Chile, at locations covering latitudes extending from 53°S to 18° S. Here we report the first measurements obtained by this network providing evidence that UVB increases are detected at these latitudes during the last Austral spring.Facultad de Ciencias Exacta

Ground-Based Ultraviolet-Radiation Measurements during Springtime in the Southern Hemisphere

We report the first measurements obtained by a network of UV-B detectors established through Argentina and Chile, at locations covering latitudes extending from 53°S to 18° S. Evidence that UVB increases are detected at these latitudes during the Austral spring 1993 is presented

Ground-based ultraviolet-radiation measurements during springtime in the Southern hemisphere

We report the first measurements obtained by a network of UV-B detectors established through Argentina and Chile, at locations covering latitudes extending from 53°S to 18° S. Evidence that UVB increases are detected at these latitudes during the Austral spring 1993 is presented. The destruction of the stratospheric ozone layer is generally considered one of the most serious environmental problems. It has been recently published that during October 1998 the ozone hole has been the deepest ever recorded. Reduction of the stratospheric ozone layer was un ambiguously detected about two decades ago in the Antarctic continent. Since then it has been systematically monitored by different means (satellite, balloon soundings and ground station observations. One of the most serious content reduction is the increase of biologically effective ultraviolet doses, particularly the so-called ultraviolet B radiation (280-320 nm) received at the Earth surface, with multiple possible hazards for living species. Despite these consequences, ground stations to check the UV Sun radiation are not very numerous, particularly outside the circumpolar area in the Southern Hemisphere. With the aim of studying whether the ozone depletion over the Antarctic area has extended further, and whether the possibility that UV radiation increase may begin to affect inhabited regions, a network of UVB detectors has been established through Argentina and Chile, at locations covering latitudes extending from 53°S to 18° S. Here we report the first measurements obtained by this network providing evidence that UVB increases are detected at these latitudes during the last Austral spring.Facultad de Ciencias Exacta

The luminescent quantum efficiency of latexCr3+latex Cr ^{3+} ions in co-doped crystals of latexLiNbO3:ZnOlatex LiNbO_ {3} : ZnO determined by simultaneous multiple-wavelength photoacoustic and luminescence experiments

In this paper, the luminescent quantum efficiency of $latex Cr ^{3+}$ ions in co-doped crystals of $latex LiNbO_{3} : ZnO : Cr ^{3+}$ is determined by using a method based on simultaneous multiple-wavelength measurement of photoacoustic and luminescence signal after pulsed laser excitation. The quantum efficiency found in this lattice was (10±4)%. This result was compared with the value found from the study of the lifetime in terms of the temperature of the luminescent levels involved. In this last case, two non-equivalent crystal sites were found for $latex Cr^{3+}$ ions, and two fluorescence quantum yields were determined. After the estimation of the concentration of each site by electron paramagnetic resonance experiments, the averaged fluorescence quantum yield value was (9±2)% in agreement with the previous result