Study of UV fluorescences induced from 4f3 T 4f25d multistep absorptions of Nd3+ions in YLiF4 and LuLiF4 crystals (original) (raw)
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Journal of Applied Physics, 2004
Ultraviolet (UV) fluorescence of Nd3+ ions induced by multistep laser excitation was investigated in Nd-doped LiYF4 and LiLuF4 crystals using a technique of time-resolved spectroscopy. The observed UV luminescence was due to transitions between the bottom of 4f25d configuration and the 4f3 states of Nd3+ ions. The first absorption band of 4f25d configuration, which starts around 56 700 cm-1, was excited by three stepwise absorptions of photons in the green (500-535 nm) from a short pulse laser excitation leading to broad emission bands in UV range (180-280 nm). An excitation band in the blue (468-486 nm) was observed due to the excitation of the second absorption band of 4f25d configuration around 63 000 cm-1 according to the photon absorption sequence: 4I9/2+hν(480 nm)-->2G(1)9/2+hν(480 nm)-->2F(2)7/2+hν(480 nm)-->4f25d(second). The observed UV emissions (180-280 nm) from the bottom of the 4f25d configuration (first state) have a lifetime of 35 ns (parity allowed) and are broadband in contrast to UV emissions from 4f3 configuration, which are also present in the luminescence investigation but having a longer lifetime (8.5 μs) and structures composed of narrow lines. The excitation spectrum of fast UV luminescence exhibited different structures depending on the excitation geometry (σ or π) with respect to the c axis of the crystal. We observed two emissions from the first state of 4f25d configuration with peaks at 535 and 595 nm modifying the luminescence branching ratio of the bottom of the 4f25d configuration around 55 500 cm-1. The equivalent cross section of three and two excitation processes was estimated at 510 nm by solving the rate equations of the system under short laser excitation, which shows that is possible to have laser action under pulsed laser pumping with intensity below the crystal damage threshold.
Investigation of energy shift of 4f3 and 4f25d levels in Nd-doped YLF and LLF crystals 1 2
Exacta, 2008
We observed UV luminescence from 4f 2 5d and 4f 3 configuration in Nd doped YLF and LLF crystals induced by multiphotonic excitation of the three photons (532nm).The LLF lattice is more compact than the YLF crystal and favours an absorption and emission shift of the main peaks due to crystal field strength . The red (and blue ) shfitings of the emission bands towards to lower (and higher) energy are different for the transitions from 4f 3 and 4f 2 5d levels. The 4f 3 transitions have smaller shift (~5 times smaller than the shift of the 4f 2 5d) due to 5s 2 5p 6 closed-shell shielding effect. On the other hand the 4f 2 5d transitions are more susceptible to lattice change. The effect of the crystalline field was compared for both lattice. The resut shows that these emission bands from 4f 2 5d configuration always shift to lower energy when substituting the Y 3+ by Lu 3+ (i.e, the last one has the ionic radius 5% smaller than Y 3+ ).
Exacta, 2008
We observed ultraviolet (UV) luminescence from 4f 2 5d and 4f 3 configuration in Nd-doped YLiF 4 (YLF) and LuLiF 4 (LLF) crystals induced by multiphotonic excitation of the three photons (532 nanometers [nm]). The LLF lattice is more compact than the YLF crystal and favours an absorption and emission shift of the main peaks due to crystal field strength. The red and blue shifts of the emission bands towards to lower (and higher) energy are different for the transitions from 4f 3 and 4f 2 5d levels. The 4f 3 transitions have smaller shift (~5 times smaller than the shift of the 4f 2 5d) due to 5s 2 5p 6 closed-shell shielding effect. On the other hand the 4f 2 5d transitions are more susceptible to lattice change. The effect of the crystalline field was compared for both lattice. The result shows that these emission bands from 4f 2 5d configuration always shift to lower energy when substituting the Y 3+ by Lu 3+ (i.e., the last one has the ionic radius 5% smaller than Y 3+).
Investigation of energy shift of 4f 3 and 4f 2 5d levels in Nd-doped YLF and LLF crystals
2006
We observed UV luminescence from 4f 2 5d and 4f 3 configuration in Nd doped YLF and LLF crystals induced by multiphotonic excitation of the three photons (532nm).The LLF lattice is more compact than the YLF crystal and favours an absorption and emission shift of the main peaks due to crystal field strength . The red (and blue ) shfitings of the emission bands towards to lower (and higher) energy are different for the transitions from 4f 3 and 4f 2 5d levels. The 4f 3 transitions have smaller shift (~5 times smaller than the shift of the 4f 2 5d) due to 5s 2 5p 6 closed-shell shielding effect. On the other hand the 4f 2 5d transitions are more susceptible to lattice change. The effect of the crystalline field was compared for both lattice. The resut shows that these emission bands from 4f 2 5d configuration always shift to lower energy when substituting the Y 3+ by Lu 3+ (i.e, the last one has the ionic radius 5% smaller than Y 3+ ).
Journal of Physics Condensed Matter, 2003
The 5f 3 → 5f 2 6d absorption spectrum of U 3+ in LiYF 4 has been well calculated using the model proposed by Reid for calculations of 4f N ↔ 4f N −1 5d spectra. The relevant formulae for the matrix element calculations which were omitted in this model are now described in detail, and the values of the direct and exchange coefficients associated with the f-d Coulomb interactions within the f 2 d configuration are derived and listed. The amount of reduction for the f-d Coulomb interaction parameters from the free-ion values is found to be ∼67%, which is much larger than the value of 26% for the isoelectronic Nd 3+ lanthanide ion in the same host.
Optical spectra of U3+ and U4+ in LiYF4 crystals
Journal of Luminescence, 1994
Optical studies on single crystals ofU: LiYF4 grown by the Czochralski method are carried out. Absorption spectra in UV, visible and IR performed at room and low temperature are characteristic of tetravalent uranium. Under reducing conditions, single crystals of U : LiYF4 are brown and the absorption spectra exhibit a strong large band around 500 nm typical of the f-d transitions of U 3 + (5f3 configuration) while the bands in the IR between 2000 and 2400 nm correspond to the absorption of the 4Iii2 state. From the analysis of the IR emission spectra between 1900 and 3000nm at 300 and 10K, the level scheme of 192 and 1112 has been deduced.
Study of optical and dosimetric properties of doped fluoride crystals
Optical Materials, 2001
Optical properties and radiation eects of various¯uoride crystals and their possible application to solid state dosimetry were studied. In particular optical absorption, PL, OSL, TL and OSTL of LiKYF 5 and LiKYF 5 :Pr 3 crystals were measured and compared to those of pure and Eu 3 -doped LiF. After X-or b-irradiation of LiKYF 5 :Pr 3 a strong TL was recorded. In samples irradiated at RT also an OSTL could be stimulated at LNT; the stimulation maximum for the OSTL was at 442 nm. The traps responsible for the TL were stable to about 600 K. In LiF: Eu 3 the TL could also be excited by VUV radiation. The VUV excited TL had excitation maxima near 125 and 190 nm. An OSTL emission was recorded in pure irradiated LiF crystals; and had an excitation maximum at 190 nm, indicating that the TL in the doped samples and the OSTL in the pure crystals are due to the same trapping states. Prolonged illumination into the F-band caused in LiF a decrease of the M-luminescence and an increase of the R -emission, which is apparently due to an M to R conversion. The dose dependence of the TL in LiKYF 5 :Pr 3 was found to be linear for b doses to above 2 kGy. The TL sensitivity of the powdered LiF:Eu 3 samples was an order of magnitude greater than that of pure LiF crystals, but by an order of magnitude lower than that of the known ecient LiF:Mg Ti (TLD-100) phosphor. The sensitivity of LiKYF 5 :Pr 3 crystals were of the order of the TLD-100 phosphor. Ó (N. Kristianpoller). 0925-3467/01/$ -see front matter Ó 2001 Elsevier Science B.V. All rights reserved. PII: S 0 9 2 5 -3 4 6 7 ( 0 0 ) 0 0 0 6 5 -3