Two-photon laser-induced fluorescence and “2+1” multiphoton ionization of silicon atoms

Two-photon laser-induced fluorescence and “2+1” multiphoton ionization detection of silicon (³P_^j″,¹D₂) atoms was accomplished using the 4 ³P_J'←3 ³P_j″, 4 ³S₁→ 3 ³P_J′, and the 4 ¹D₂→ 3 ¹D₂ resonant two-photon transitions. Silicon atoms were produced in their ground ³P_J″ (J″ = 0,1,2) and first singlet ¹D₂ states by the multiphoton dissociation of Si(CH₃)₄ in the wavelength region 400–460 nm. Line strength intensities for the two-photon transitions originating from the 3 ³P_J″ (J″ = 0,1,2) states were calculated and compared to experimental values determining that the silicon (³P_J″) atoms were produced in a statistical population distribution.     

Isotope Shifts of Nitrogen around 800 nm

The Doppler-limited absorption spectra of ¹⁴N and ¹⁵N atoms were measured around 800 nm using concentration modulation spectroscopy to study their isotope shifts. The nitrogen atoms were generated by discharging molecular nitrogen buffered with helium in a homemade discharge tube. The isotope shifts of four multiplets (3s⁴P_J→3p⁴D_J^o, 3s⁴P_J→3p⁴P_J^o, 3s²D_J→5s²P_J^o, and 3p²P_J^o→5s²D_J^o) were measured and their J-dependent specific mass shifts were observed and discussed.     

Autoionization resonances in atomic Ga,In, and Pb

Autoionization resonances of the type (n?1)d→np, wheren pertains to the outermost shell of Ga, In and Pb, were studied with the use of electron spectrometry in combination with synchrotron radiation. The relative strengths of the exit channels for the various resonance states were measured. In the case of Ga and In, a complete partitioning of the total absorption cross section into thes ^{2 1} S,sp ¹ P, andsp ³ P components (exit channels) was achieved, and in the case of Pb the decay of the resonance states into the major exit channels 6s ² 6p ² P _1/2, 6s ² 6p ² P _3/2, 6s 6p ^{2 4} P _1/2, 6s 6p ^{2 2} D _3/2 and 6s 6p ^{2 2} P _1/2 was determined. In Ga, strong coupling was observed for those states of the 4p ² manifold that have the same symmetries as the final ionic states, e.g. 4p ^{2 3} P→4s 4p ³ P and 4p ^{2 1} S→4s ^{2 1} S. In In, there is a similar, but weaker correlation, which also includes two-electron excitation channels. Comparison between Ga and In shows that thesp ³ P channel is much stronger in In (52% vs 40% in Ga) while thesp ¹ P channel is correspondingly weaker (28% vs 37%), with thes ^{2 1} S channel remaining practically unchanged (20 vs 23%). In Pb, the 6s ² 6P ² P _1/2 channel displays interference patterns due to a strong, competing direct transition, whereas the other channels do not, indicating population predominantly via the resonance states.     

Constructing novel red-emitting Ba2Y0.8Eu0.2NbO6:Mn4+ phosphors for multi-type luminescent thermometers and high-security anti-counterfeiting films

To date, luminescent materials have been preferably used for non-contact optical thermometers. In this manner, novel red-emitting Ba₂Y_0.8Eu_0.2NbO₆:Mn⁴⁺ (BYEN:Mn⁴⁺) phosphors were designed for multi-type non-contact luminescent thermometers based on the dual-emission states and temperature-dependent lifetime (TDL) models. In the temperature range of 303–483 K, the sensing sensitivities based on the dual-emission states of (⁵D₀→⁷F₂, ²E_g→⁴A_2g) and (⁵D₀→⁷F₁, ²E_g→⁴A_2g) were estimated. Especially, the maximum absolute sensing sensitivity (S_a) was found to be about 0.1558 K^-1 for the BYEN:0.007Mn⁴⁺ phosphor based on the ⁵D₀→⁷F₁ and ²E_g→⁴A_2g positions. This phosphor also exhibited good relative sensing sensitivity (S_r) (0.0186 K^-1) based on the ⁵D₀→⁷F₂ and ²E_g→⁴A_2g states. Besides, the relative sensing sensitivities (S_R) at ⁵D₀→⁷F₁ and ²E_g→⁴A_2g transitions were estimated to be 0.0034 and 0.0194 K^-1, respectively with the help of the TDL technique. In the light of these results, novel red-emitting Ba₂Y_0.8Eu_0.2NbO₆:Mn⁴⁺ phosphors are expected to be a potentially attractive candidate for applications in multi-type luminescent thermometers. Finally, a novel unique polydimethylsiloxane film exhibiting tricolor-luminescent emissions was introduced and further suggested for high-security anti-counterfeiting.     

Crystal Structure and Vibrational Spectrum of Dipotassium Manganese(II) Hexathiodiphosphate(IV), K2Mn[P2S6]

K₂Mn[P₂S₆] was synthesized from the elements in sealed quartz ampoules at 1 173 K. The compound forms transparent light brown crystals, stable against air and moisture. The crystal structure (monoclinic; space group P2₁/n, No. 14; a = 6.1966(9), b = 12.133(2), c = 7.424(1) Å, β = 101.52(1)°, Z = 2; Pearson code mP22) consists of columns of face-sharing S₆ polyhedra (distorted octahedra and trigonal antiprisms) parallel to the a axis, interconnected by inserted K⁺ (CN 10; d(K? S) = 3.23–3.92 Å). The S₆ polyhedra of the columns are centered alternately by Mn (in octahedra with d?(Mn? S) = 2.647 Å) and P₂ pairs (in trigonal antiprisms) which are inclined to the a axis by 73.1°. The bond lengths in the resulting hexathiodiphosphate(IV) anions, [P₂S₆]^4?, with approximate 3 2/m–D_3d symmetry, are d(P? P) = 2.211 Å and d(P? S) = 2.018 Å. K₂Mn[P₂S₆] is isotypic to K₂Fe[P₂S₆], being the second member of this structure type. The internal modes of the observed Raman and FIR/IR spectra of K₂Mn[P₂S₆] are in accord with the factor group analysis, and the fundamentals are assigned on the basis of [P₂S₆]^4? units, taking into account the deviation of the D_3d symmetry.     

Hyperfine structure and Zeeman effect studies in the 6p7p-6p7s transitions in Bi II

The hfs and hfs Zeeman splitting of nine lines from the array 6p7p→6p7s as well as lines λ = 496.9 nm (6p8p ³D₂→6p7s ³P₂) and λ=581.8 nm (6p8s ³P₀→6p7p ³D₁) of Bi II have been analysed. The Zeeman effect studies were performed for transverse direction of observation and separated π; and σ components of lines. The electrodeless discharge tube containing metallic Bi was used as the light source. The spectral apparatus consisted of a sliver-coated Fabry-Perot etalon and a grating spectrograph combined with a diode array detector. In the analysis of the spectra we used the computer simulation technique. The magnetic-dipole (A) and the electric-quadruple (B) hfs constants as well as Lande-g_j factors for the level 6p8p ³D₂ and all levels of configurations 6p7s and 6p7p (with the exception of 6p7p ³S₁) were determined. Our results are compared with recent theory and other experiments.     

Comprehensive study on compositional modification of Tb3+ doped zinc phosphate glass

Series of glass composition (60-x) P₂O₅ -40 ZnO –(x) Tb₂O₃ where x = 0.5, 1.0, 1.5, 2.0, 2.5 and 3.0 mol % are prepared by conventional melt quenching technique. X-Ray Diffraction (XRD), FTIR, UV-Vis-NIR and the photoluminescence (PL) spectroscopy are used to characterize the physical, structural and optical behavior of the glass sample. The XRD pattern confirms the amorphous nature and DTA verified the thermal stability of all the glass samples. Glass with 1.5 mol % of Tb₂O₃ possesses the highest thermal stability. Glass density is found to increase proportionally with increasing amount of Tb³⁺ while the molar volume behaves reversely. Six main IR absorption bands centered at about 540, 748, 891, 1085 and 1294 cm^{− 1} are evidenced. The UV-Vis NIR absorption spectra reveals the absorption center band at about 540, 376, 488 and 1920 nm corresponding to the absorption from ⁷F₆ ground state to various excited state of Tb³⁺ ion. The optical band gaps for direct and indirect transition are in the range 4.53–5.07 eV and 4.30 eV-4.56 eV respectively. The Urbach energy decreases with the increasing concentration of Tb₂O₃. The PL emission spectra reveals several prominent peaks at 413, 435, 457, 488, 540, 585 and 620 nm due to electronic transition from ⁵D₃→⁷F₅, ⁵D₃→⁷F₄, ⁵D₃→⁷F₃, ⁵D₄→⁷F₆, ⁵D₄→⁷F₅, ⁵D₄→⁷F₃ and ⁵D₄→⁷F₅ respectively.     

Tunable luminescence and energy transfer process between Tb3+ and Eu3+ in GYAG:Bi3+, Tb3+, Eu3+ phosphors

A series of Eu³⁺ ions co-doped (Gd_0.9Y_0.1)₃Al₅O₁₂:Bi³⁺, Tb³⁺ (GYAG) phosphors have been synthesized by means of solvothermal reaction method. The XRD pattern of GYAG phosphor sintered at 1500 °C confirms their garnet phase. The luminescence properties of these phosphors have been explored by analyzing their excitation and emission spectra along with their decay curves. The excitation spectra of the GYAG:Bi³⁺, Tb³⁺, Eu³⁺ phosphors consists of broad bands in the shorter wavelength region due to 4f⁸ → 4f⁷5d¹ transition of Tb³⁺ ions overlapped with 6s² → 6s¹6p¹ (¹S₀ → ³P₁) transition of Bi³⁺ ions and the charge transfer band of Eu³⁺–O^2?. The present phosphors exhibit green and red colors due to ⁵D₄ → ⁷F₅ transition of Tb³⁺ ions and ⁵D₀ → ⁷F₁ transition of Eu³⁺ ions, respectively. The emission was shifted from green to red color by co-doping with Eu³⁺ ions, which indicate that the energy transfer probability from Tb³⁺ to Eu³⁺ ions are dependent strongly on the concentration of Eu³⁺ ions.     

Study on the Geometric and Electronic Structures of Al<Subscript><Emphasis Type="Italic">n</Emphasis></Subscript>Si<Subscript><Emphasis Type="Italic">m</Emphasis></Subscript> (n = 3, 4, 5; m = 1, 2, 3, 4) Clusters

Genetic algorithm combined with the semi-empirical Hamitonian AM1/PM3 is used to search the low energy isomers of Al _n Si _m (n = 3, 5, m ≤ 3 and n = 4, m ≤ 4) and the charged clusters with 20 and 28 valence electrons. The candidate structures were optimized by the density functional theory PBE0 and B3LYP models with the triply split basis sets including polarization functions. The electronic structures show that Al–Si binary clusters behave like metal clusters. The molecular orbitals accord with that predicted by the jellium model, and the electron localization function shows the valence electrons are delocalized over the entire clusters. The clusters having 20 and 28 valence electrons exhibit pronounced stabilities and large energy gaps. The 20 valence electrons of Al₄Si₂ and Al₃Si₃ ⁺, Al₅Si^? form closed shells 1S ²1P ⁶2S ²1D ¹⁰. Al₄Si₄ and Al₅Si₃ ^? have oblate structures and the P, D, F levels spilt considerably in these clusters. The electron density distributions suggest that doping silicon in the aluminum clusters enhances the stability considerably.     

Alignment of double vacancy states (1s2p)−1 3 P and1 P of neon for electron impact ionization

From intensity of Auger transitions (1s2p)^{?1 1} P,³ P→2p ^{?3 2} P,² D+e _A ^? relative to 1s ^{?1 2} S→2p ^{?2 1} D+e _A ^? measured at ?=54 and 90° relative to the primary electron beam we have determined the alignment of double vacancy states (1s 2p)^{?1 1} P and³ P of neon for electron impact ionization for the impact energies 1.5, 2.0, 2.5 and 4.0 keV. ForE ₀=1.5, 2.0 and 2.5 keV the alignment is compatible with zero with an upper limit of , forE ₀=4.0 keV a small negative value was found.     

Oscillator strength measurements of the 5s5p 3P1 → 5snd 3D2 Rydberg transitions of cadmium

We report oscillator strengths distribution in the bound region of cadmium corresponding to the 5s5p ³P₁ → 5snd ³D₂ (21 ≤ n ≤ 52) Rydberg transitions. The experiment was performed using two frequency doubled dye lasers simultaneously pumped by a common Nd:YAG laser in conjunction with an atomic beam set-up. The absolute photoionization cross section of the 5s5p ³P₁ intermediate state at the 5s ²S_1/2 ionization threshold has been measured as 20 (4) Mb using the saturation technique. The measured value of the photoionization cross section at threshold is used to extract the f-values of the above mentioned Rydberg transitions.     

Absorption and photoluminescence spectra of Tm3+-doped fluorophosphate glasses

We have carried out absorption and photoluminescence spectra of six newly prepared TmF₃ (2 M%) doped fluorophosphate glasses of composition: (NaPO₃)6BaF₂ZnF₂RF where R = Li, Na, K, (LiNa), (NaK) and (KLi). By evaluating the Judd—Ofelt intensity parameters for the measured absorption levels, the recorded photoluminescence spectra have been analysed to estimate the fluorescent radiative properties (A, A_T, β_R) and the stimulated emission cross-sections (σ^E_P) of the following luminescence transitions:¹G₄→³H₆ (λ=451 nm)¹D₂→³H₄ (λ=468 nm)³P₀→³F₂ (λ=482 nm)¹D₂→³H₅ (λ=492 nm)These have been determined in order to understand the alkali effects on the Tm³⁺-optical glasses studied.     

Optical Spectroscopy of Pr3+ Ion Singly Doped LiLuF4 Single Crystal by Bridgman Method

High quality LiLuF₄ single crystals doped with various Pr³⁺ ions were synthesized by a vertical Bridgman method in completely sealed platinum crucibles. The excitation spectra spans from 420 nm to 500 nm. The prepared single crystals exhibit a blue band at 480 nm (³P₀→³H₄), a green band at 522 nm (³P₁→³H₅), and a red band at 605 nm (¹D₂→³H₄) when excited at 446 nm; their corresponding average lifetimes are 38.5 μs, 37.3 μs, and 36.8 μs, respectively, which are much longer than those in oxide single crystals. The effects of excitation wavelength and doping concentration on emission intensities and chromaticity coordinates are investigated. The optimal Pr³⁺ concentration is confirmed to be 0.5%. The temperature dependent emission shows that the emission intensity constantly decreases with the increase of temperature from 298 K to 443 K due to the enhancement of non-radiative quenching at high temperature. The ³P₀→³H₄ transition is the most vulnerable to temperature, followed by the ³P₁→³H₅ transition and ¹D₂→³H₄ transition.     

Synthesis,crystal structure,magnetism and vibrational spectrum of Dipotassium Iron(II) Hexathiodiphosphate(IV), K2Fe[P2S6]

K₂Fe[P₂S₆] was synthesized from the elements at 1173 K in sealed quartz tubes. The compound forms transparent orange crystals, stable against air and moisture. K₂Fe[P₂S₆] crystallizes in the monoclinic system, space group P2₁/n (No. 14), with cell dimensions (T = 298.5 K) a = 6.0622(4), b = 12.172(1) and c = 7.3787(8) Å, β = 101.113(7)°, Z = 2. The novel structure type (mP22) is characterized by columns of alternating face-sharing S₆ octahedra and trigonal antiprisms (both distorted) parallel to the a axis, which are interconnected by inserted K⁺ (CN 10; {2,6,2}-polyhedra; d(K? S) = 3.231 ? 3.845 Å). The S₆ polyhedra of the columns are centered alternately by Fe (d?(Fe? S) = 2.577 Å) and P₂ pairs which are inclined to the a axis by 73.4°. The bond lengths in the hexathiodiphosphate(IV) anions, [P₂S₆]^4?, with approximate 3 2/m – D_3d symmetry, are d?(P? P) = 2.20 and d?(P? S) = 2.02 Å. The compound is paramagnetic above T_N = 28 K with μ = 4.69 B.M. and orders antiferromagnetically below T_N. The internal modes of the observed Raman and FIR spectra of K₂Fe[P₂S₆] are in accord with the factor group analysis, and the spectra are assigned on the basis of [P₂S₆]^4? units, taking into account the deviation from D_3d symmetry.     

Diffusion of resonance radiation in atomic vapor imaging

The effect of resonance radiation diffusion due to radiation trapping has been studied in an atomic vapor imaging filter. Using a cesium resonance fluorescence imaging monochromator, the spatial distortions due to resonance radiation trapping by Cs atoms in the pumping/imaging region have been investigated. It was found that the spatial distortions were dependent on the number density of the Cs atoms, as well as the irradiance of the signal photons at 852.12 nm (6²S_1/2→6²P^o_3/2). The pump laser (917.23 nm, 6²P^o_3/2→6²D_5/2) did not influence the radiation diffusion to the same degree as the signal beam. It is shown that there is a compromise between maximum optical density and spatial resolution. The number density of the Cs resonance fluorescence imaging monochromator was optimized to obtain the highest spatial resolution and signal-to-background ratio.     

Identification of low molecular vaporizable components in silicone resins using gas chromatography/mass spectrometry

Silicone resins can be used as polymeric precursors in the production of ceramic materials. Cohydrolysis of mixtures of trimethylchlorosilane, methyldichlorosilane, vinylmethyldichlorosilane and phenyltrichlorosilane leads to the formation of especially suitable polysiloxanes, but also low-molar mass siloxanes are formed as undesired by-products. The structures of these by-products have been elucidated. Vaporizable components of the matrix have been isolated by distillation, separated using gas chromatography and identified by mass spectrometry in EI (electron impact ionization) and CI (chemical ionization with isobutane) mode. The EI mass spectra of the siloxane oligomers with different numbers of Si-H, Si-phenyl and Si-vinyl groups show characteristic fragments like Me₃Si⁺, ViMe₂Si⁺, Vi₂MeSi⁺, PhMe₂Si⁺, and Ph₂MeSi⁺, which give a first indication to the structure, but generally do not show molecular peaks. A reliable determination of the molar mass has been possible considering the CI-ions and CI-fragments [M+1]⁺, [M−1]⁺, [M−27]⁺ and [M−77]⁺, respectively. The compounds M₂D^Ph,OH and M₃T^Ph have been identified as main components of the investigated siloxane mixture. Besides, numerous linear compounds of the type M₂(D^H)n(D^Vi)_m and M₂T^Ph(D^H)_n(D^Vi)_m M as well as cyclic ones of the structure [MT^Ph(D^H)_n(D^Vi)_m] with n, m=0–3 have been indicated. Received: 3 March 1995/Revised: 25 March 1995/Accepted: 3 April 1995     

刺乌头碱氢溴酸盐的合成及晶体结构

报道了以双溴代烷烃和刺乌头碱合成刺乌头碱氢溴酸盐的方法. 用元素分析、红外光谱、高分辨质谱和核磁共振进行了表征. 并用X射线单晶衍射确定了标题化合物的绝对构型. 晶体结构表明, 该化合物通过分子间氢键形成了网状类似超分子结构. 晶体属于单斜晶系, P2₁空间群, 晶胞参数: a＝1.0619(2) nm, b＝1.2196(3) nm, c＝1.2282(2) nm, β＝90.87(1)°, V＝1.59037(54) nm³, Z＝2, D_m＝1.428 g/cm^－3, F(000)＝720.0, µ＝1.349 mm^－1. 环 A, B, C, D, E和F分别呈船式、椅式、信封式、船式、船式和信封式. 其绝对构型被确定为1S,4S,5S,7S,8S,9S,10S,11S,13R,14S,16S,17R.     

Vibration spectrum and normal coordinate analysis of the pyrothiophosphates Na4P2S7, Na2FeP2S7, and Ag4P2S7

Na₄P₂S₇, Na₂FeP₂S₇, and Ag₄P₂S₇ were prepared by elemental synthesis at high temperatures and were characterized by vibration spectra and differential thermal analysis (DTA). A normal coordinate analysis was performed for P₂S⁴⁻₇. Additional vibration frequencies indicate the presence of the decathiotriphosphate anion P₃S⁵⁻₁₀. The formation of higher thiophosphates of the type P_nS^(n+2)-_3n+1 with n ≥ 4 cannot be excluded.     

Phosphane/phosphite silver(I) carboxylates as CVD precursors

The preparation of [L_mAgO₂CR] (L = PⁿBu₃, P(OMe)₃, P(OEt)₃; m = 1, 2; R = singly-bound organic group) and [L_mAg–E–AgL_m] (L = PⁿBu₃; E = oxalate; m = 1, 2, 3) is described. Their use as spin-on and CVD precursors is reported. SEM and EDX studies show that closed and homogeneous silver films with admirable conductivity could be obtained.     

A mass spectral study of some symmetric and unsymmetric sulfides,disulfanes, and trisulfanes

The low-resolution mass spectra of 13 trifluoromethyl and/or methyl sulfur-containing compounds (CF₃S_nCF₃, CF₃S_nCH₃, CH₃S_nCH₃, CF₃S_mCl, and CH₃S_mCl; n = 1, 2, 3; m = 1, 2) are reported and discussed. There is a considerable similarity between the fragmentation pattern of compounds with the same terminal groups. However, with a fluorinated and a non-fluorinated methyl group, the major fragmentation products produced are similar to those for the dimethyl compounds.