Time-resolved site-selection spectroscopy studies of NdAl3(BO3)4 crystals

A pulsed, tunable dye laser was used to selectively excite Nd³⁺ ions in nonequivalent crystal field sites in NdAl₃(BO₃)₄ crystals and energy transfer between ions in different types of sites was studied by monitoring the time evolution of the fluorescence spectrum. The results show that the energy transfer rate varies as t^{$\text{-1}\text{2}$} and increases with temperature. The predictions of various models of phonon-assisted energy transfer are compared to the results.     

Relaxation of the 4G92 state of Nd3+ in LaCl3 and Nd3+ in La(Cl99.6Br0.4)3

The decay of the ⁴G_{$\text{9}\text{2}$} state of Nd³⁺ in LaCl₃ and La(Cl_99.6 Br_0.4)₃ was measured after pulsed laser excitation as a function of temperature. The decay rate is shown to depend besides the radiative transition on single-phonon relaxation between the states ⁴G_{$\text{9}\text{2}$} ($\text{μ =}\text{1}\text{2}$) and ⁴G_{$\text{9}\text{2}$} ($\text{μ =}\text{3}\text{2}$) and on multiphonon orbit-lattice relaxation from ⁴G_{$\text{9}\text{2}$} to ²G_{$\text{9}\text{2}$}. Partial substitution of Cl by Br only alters the radiative lifetime.     

Generation of narrowband tunable VUV radiation at the Lyman-α wavelength

Tunable narrowband VUV radiation has been generated at the Lyman-α wavelength $\text{λ =}\text{1216}\text{\&}\text{A}\text{ring}$; by frequency tripling in krypton the frequency-doubled output of a powerful dye laser system which is excited with the second harmonic of a Nd-YAG laser. 5 ns long UV dye laser pulses ($\text{λ =}\text{3646}\text{A}\text{?}$) of 1.8 MW peak power yielded VUV light pulses of 2.2 W (5.4 × 19⁹ photons/pulse). The bandwidth of the dye laser radiation could be narrowed to 8.7 × 10^-3cm^-1 (4.6 × 10^-3 Å). The expected bandwidth of the VUV is less than 5.2 × 10^-2cm^-1 (7 × 10^-4 Å). The tunable VUV radiation is used for the recording of the absorption spectra of the Lyman-α resonance transitions in atomic hydrogen and deuterium with doppler-limited resolution.     

Multiphonon relaxation rate from pumped level to upper laser level in YAG:Nd

The rise time of the near-infrared fluorescence intensity has been measured in YAG:Nd³⁺ at room temperature under the excitation by 10 ns duration pulses at 514.5 nm using a time-correlated single photon counting method. The result reveals that the relaxation rate from the pumped level (${}^2\text{K}{}_{\mathrm{<mtext>13</mtext><mtext>2</mtext>}}$ + ${}^2\text{G}{}_{\mathrm{<mtext>9</mtext><mtext>2</mtext>}}$ + ${}^4\text{G}{}_{\mathrm{<mtext>7</mtext><mtext>2</mtext>}}\text{)}$ to the upper level laser level $\text{(}{}^4\text{F}{}_{\mathrm{<mtext>sol3</mtext><mtext>2</mtext>}}\text{)}$ is larger than 10⁸s^?1, which is in contrast with the previously reported values of (1.6 ～ 2) × 10⁶s^?1. An experiment to search for the visible emission in YAG:Nd³⁺ gives support to the present value.     

Laser time-resolved selective excitation of Nd3+ ions in KNdP4O12 crystals

The emission spectra of Nd³⁺ ions in KNd_xRE_1?xP₄O₁₂ (RE = Y, La and Pr) and KNd_xCr_1?xP₄O₁₂ crystals were investigated. Under selective excitation into ²G$\text{7}\text{2}$ + ⁴G$\text{5}\text{2}$ multiples at 1.6 K the fluorescence of Nd³⁺ ions in non-equivalent crystal sites was observed. The excitation spectrum of the ${}^4\text{F}\text{3}\text{2}$ fluorescence had a complex satellite structure. Time resolved measurements showed the dependence of the fluorescence decay on the excitation wavelength. Selective excitation into the satellite lines at the wings of the main transition led to strongly non-exponential decay. The low temperature results indicated that there is no spectral energy transfer between ions in different types of sites.     

Excitation processes leading to ruby emission

We excited the ²T₁-levels in ruby by tunable laser light, pumped bya pulsed YAG:Nd³⁺ laser, and observed the low temperature emissions from the 2$\text{A}$ and $\text{E}$ sublevels of ²E in the mild bottlenecking regime. The R₂-line decay time was about five-fold longer and the ratio of intensities R₂/R₁ higher (by up to a factor 10) than after pumping into ⁴T₂. It is suggested that when ⁴T₂ is pumped the relaxation is nonadiabatic, so that transitions between the sublevels occur while the ²E state relaxes to its normal (trigonal) configuration. The time-development of the relaxing state is studied. It is shown that its coherence between the 2$\text{A}$ and $\text{E}$ sublevels leads to a narrowing of the spectral width in transition between the sublevels.     

Oscillator strengths of the first forbidden lines of rubidium

The oscillator strengths of the 5s-4d first forbidden lines of rubidium at 5165 Å were determined by performing CW tunable dye laser absorption measurements. Measured oscillator strengths of 8.06±0.48×10^-7 and 5.38±0.31×10^-7 for the ²D_{$\text{5}\text{2}$} and ²D_{$\text{3}\text{2}$} states, respectively, are compared with previously published values.     

掺Nd3+激光玻璃的激光窄线选择激发

本文利用可调谐脉冲染料激光器的窄线输出,在低温和室温下,激发掺钕碲、锗、硅、磷酸盐玻璃和氟铍玻璃的⁴I_9/2→⁴G_5/2(²G_7/2)不均匀增宽吸收带。观测了荧光衰减对激发波长的关系,从而研究在不同玻璃基质中,处于不同格位的Nd³⁺离子的衰减特性以及他们之间的相互作用情况。 关键词：     

Tunable XUV radiation generated by nonresonant frequency tripling in neon

Nonresonant frequency tripling of ultraviolet (UV) radiation (λ_uv = 216–223 nm, generated by sum frequency mixing of the outputs of a frequency doubled pulsed dye laser and of the Nd-YAG pump laser) generates in neon coherent light in the extreme ultraviolet (XUV). The XUV radiation is tunable in spectral regions of negative dispersion λ_xuv = 72.05- 73.58 nm and λ_xuv = 74.3–74.36 nm at the high energy side of the transitions $\text{2p-3s′[}\text{built1}\text{2}\text{, 1]}$ and $\text{2p-3s[}\text{built3}\text{2}\text{, 1]}$. At UV input powers of 0.1-0.3 MW the generated XUV power was typically P_xuv = 0.1-0.4 W (1.5–6 x 10⁸ photons/pulse). Since present UV dye laser systems provide at λ_uv pulse powers of almost 1 MW the XUV output could easily be increased by more than one order of magnitude.     

Excess Gibbs energy for six binary solid solutions of molecularly simple substances

In this paper we apply the method developed in a previous study of Ar + CH₄ to the evaluation of the excess Gibbs energy G^{E S} for solid solutions of two molecularly simple components The method depends on combining information on the excess Gibbs energy G^{E L} for the liquid mixture of the two components with a knowledge of the (T, x) solid-liquid phase diagram Certain thermal properties of the pure substances are also needed G^{E S} has been calculated for binary mixtures of Ar + Kr, Kr + CH₄, CO + N₂, Kr + Xe, Ar + N₂ and Ar + CO. In general, but not always, the solid mixtures are more non-ideal than the liquid mixtures of the same composition at the same temperature Except for the Kr + CH₄ system, the ratio $\text{r =}\text{G}{}^{\mathrm{E\; S}}\text{G}{}^{\mathrm{E\; L}}$ is larger the richer the solution in the component with the smaller molecules     

Preferential excitation transfer in Cs1(6D32)- Cs(6S12) collisions

A cw dye laser beam, tuned near the Cs 8761 Å resonance (Cs¹(6P_{$\text{1}\text{2}$}) → Cs¹(6D_{$\text{3}\text{2}$}) transition) is focused into a Cs vapor. At a Cs density higher than 5 × 10¹⁵ cm^-3, we observe a greater 6P_{$\text{1}\text{2}$} population when the laser is on resonance than when it is off resonance. However, at a lower Cs density, the reverse is observed. This phenomenon is explained as due to the preferential excitation transfer process: Cs¹(6D_{$\text{3}\text{2}$}) + Cs(6S_{$\text{1}\text{2}$}) → Cs¹(6P) + Cs¹(6P), and the corresponding cross secti on is estimated to be (1.5^+1.5_-0.7) × 10^-14 cm² by fitting the experimental results to an approximate rate-equation analysis.     

Level-crossing under nearly monochromatic excitation by a narrow-band cw dye laser

The shape of level-crossing signals under excitation by a narrow-band tunable dye laser has been investigated. The light of the laser was scattered on a highly collimated atomic beam of Na. The laser radiation (bandwidth about 3 MHz) was fairly monochromatic compared with the natural line-width of the 3 ²P_{$\text{3}\text{2}$} state (10 MHz). The form of the zero-field level-crossing signal of this state depends strongly on the frequency of the exciting radiation. The experimental results agree well with calculated signal shapes.     

Direct ninth harmonic conversion of picosecond laser pulses

Direct ninth harmonic conversion of picosecond laser pulses is obtained for the first time. Using sodium vapor, phase- matched ten-photon process by Nd³⁺: glass laser pumping is realized. Effective ninth-order nonlinear susceptibility of the order of x⁽⁹⁾_eff ～ 10^-64 ESU is estimated.     

A frequency-doubled frequency-stabilized cw ring dye laser for spectroscopy: A study of the λ = 293.3 nm transition in In1

In this letter a frequency-doubled frequency-stabilized CW ring dye laser for the wavelength region 292–305 nm is described. 500 μW U.V. power combined with a 2 MHz linewidth and a 7 GHz scanwidth has been obtained by intracavity frequency doubling in an ADA crystal. The set-up has been tested on the hyperfinestructure of the λ = 293.3 nm transition 5p²P_{$\text{3}\text{2}$} → 7s²S_{$\text{1}\text{2}$} in In1.     

Vacuum ultraviolet luminescence from a micro-pulling-down method grown Nd:(La0.9,Ba0.1)F2.9

Vacuum ultraviolet (VUV) luminescence from a Nd³⁺:(La_1−x,Ba_x)F_3−x (x=0.1) and a Nd³⁺:LaF₃ single crystal grown by the micro-pulling-down method modified for fluoride crystal growth is discussed. Emission resulting from excitation with 157 nm pulses of a F₂ laser and by 290 nm femtosecond pulses of a Ti:sapphire laser show that the luminescence spectral and temporal characteristics are similar for both excitation cases and that they have good prospects as a VUV laser material.     

Doppler-limited dye laser excitation spectroscopy of HCF

The cw dye laser excitation spectrum of the $\text{A}\text{?}{}^1\text{A″(000) ←}\text{X}\text{?}{}^1\text{A′(000)}$ vibronic band of HCF was observed between 17 188 and 17 391 cm^?1 with the Doppler-limited resolution, 0.04 cm^?1. The HCF molecule was produced by the reaction of discharged CF₄ with CH₃F, and 853 lines were observed, of which 516 transitions were assigned to K′_a ← K″_a = 3 ← 4, 2 ← 3, 1 ← 2, 0 ← 1, 1 ← 0, 2 ← 1, 0 ← 0, 1 ← 1, 2 ← 2, 3 ← 3, 2 ← 0, and 0 ← 2 subbands. A rotational analysis yielded the rotational constants and quartic and sextic centrifugal distortion constants for both the $\text{A}\text{?}$ and $\text{X}\text{?}$ states and the band origin, with good precision. The molecular constants determined reproduce the observed transition frequencies with an average deviation of 0.0038 cm^?1. Small rotational perturbations in the excited state were found at J = 5, 6 and J = 10, 11 of J_1,J and at J = 15, 16 of J_2,J?1 levels.     

Minimum ion-ion distance,cross relaxation and excitonic behaviour in Ln3+ stoichiometric materials

Comparison of the self-quenching rates of Nd³⁺(⁴F_3/2) and Tb³⁺(⁵D₃) in two stoichiometric materials LnP₅O₁₄ and LnNa(WO₄)₂, shows opposite behaviour (Ln=lanthanides). For Nd³⁺(⁴F_3/2), LnNa(WO₄)₂ which has a small minimum Ln³⁺ -Ln³⁺ distance ($\text{R}{}_{\min }\text{= 3.9}\text{A}\text{?}$), exhibits a stronger rate than LnP₅O₁₄ ($\text{R}{}_{\min }\text{= 5.2}\text{A}\text{?}$) with respectively a quadratic and a linear concentration dependence. On the contrary, for Tb³⁺(⁵D₃), LnNa(WO₄)₂ exhibits a smaller rate than LnP₅O₁₄ with opposite concentration dependence. Showing that the coherent propagation is negligible, self-quenching is attributed essentially to cross-relaxation with fast or limited incoherent diffusion. Results clearly demonstrate that the existence of a structural isolation is only secondary to energy matching conditions. This in turn confirms the important role of the crystal field strength as exemplified by comparing NaLn(WO₄)₂ and KLn(WO₄)₂.     

Tunable XUV radiation generated by nonresonant frequency tripling in argon

Nonresonant frequency tripling of the ultraviolet (UV) radiation of a frequency doubled pulsed dye laser generates in argon coherent radiation in the extreme ultraviolet (XUV). The radiation is tunable in spectral regions of negative dispersion λ_XUV = 97.4–104.75 nm, λ_XUV = 86.8–86.98 nm and λ_XUV = 85.7–86.68 nm located at the high energy side of the transitions 3p-4s′ [$\text{1}\text{2}$,1], 3p-5s′ [$\text{1}\text{2}$,1] and 3p-3d′ [$\text{3}\text{2}$,1], respectively. At UV input pulse powers of 1–2 MW the pr oduced. XUV power was typically 1–8 W (0.2–1.6 × 10¹⁰ photons/pulse).     

A comparative study of the energy migration and energy transfer in highly doped Nd:YAG single crystal

The donor-donor (D-D) energy migration interaction parameter C_DD in high-concentration Nd³⁺-doped YAG laser crystal is estimated, for the first time, by using the Yokota-Tanimoto (Y-T) model and the spectral overlap model (SOM) of Kushida. Firstly, the experimental luminescence decay curves of ⁴F_3/2 state of Nd³⁺ ions in YAG laser crystal at room temperature for 2.0 and 3.0 at% Nd³⁺ concentrations reported by Mao are fitted successfully by using the Y-T model and the parameter C_DD is obtained to be 1.50×10⁻³⁹ cm⁶/s. Secondly, the parameter C_DD is also directly calculated by using the SOM of Kushida: C_DD is calculated to be 2.73×10⁻³⁹ cm⁶/s. By comparing the energy migration interaction parameter C_DD and the donor-acceptor (D-A) energy transfer interaction parameter C_DA (1.794×10⁻⁴⁰ cm⁶/s), it is concluded that energy migration rate between Nd³⁺ ions in YAG laser crystal was about 11 times larger than energy transfer rate, and that energy migration would play a very important role in high-concentration Nd³⁺ -doped YAG laser crystal.     

ESR and superconductivity of Nd3+ and Gd3+ in ZrIr2

We report low temperatures ESR and Superconductivity experiments on Nd³⁺ and Gd³⁺ in the superconducting cubic intermetallic compound ZrIr₂. The ratio of the squares of the effective 4f-conduction electron exchange parameters corresponding to Nd³⁺ and Gd³⁺ ($\text{J}{}^2{}_{\mathrm{s-Nd}}\text{J}{}^2{}_{\mathrm{s-Gd}}$) were extracted both from the thermal broadening of the ESR linewidths and from the initial depression of the superconducting critical temperature, and were found to be comparable. Nd³⁺ was found to have a larger exchange parameter than of Gd³⁺.