5D0 State Research Articles

Resolution of the two metal binding sites of human serum transferrin by low-temperature excitation of bound europium(III)

Derivatives of apotransferrin have been prepared in which europium replaces iron at either one or both of the two metal ion binding sites. At low temperature (77 K), pH 7.0, two sharp absorption lines are seen by means of laser-induced fluorescence of the bound europium. The one at 579.88 nm (17 245 cm-1) is assigned to the C-terminal region A site, and the other at 579.26 nm (17 263 cm-1) is assigned to the N-terminal region B site. The lifetimes of the excited 5D0 states are 210 +/- 20 and 310 +/- 30 mus for the A and B sites, respectively. The energy difference between the two peaks is a function of pH, with the splitting decreasing from 0.62 nm (18.5 cm-1) at pH 7.0 to 0.15 nm (4.5 cm-1) at pH 8.0. This spectroscopic unequivalence may be explained by a charge difference of the liganding groups at sites A and B.

Hyperfine induced perturbation of the 5s19d Rydberg state of87Sr

High-resolution two-photon spectroscopy was applied to investigate the 5s19d Rydberg level of strontium. Transitions from the 1S0 ground state to the 5s19d 3D3 state were observed for 87Sr (I=9/2), caused by local mixing between the 5snd 1D2 and 3D3 states induced by hyperfine interaction. A calculation shows excellent agreement with experiment.

Transition probability of the 1S → 1D2 emission of atomic oxygen

The transition probability of the 1S0 → 1D2 emission (5577 Å) of atomic oxygen has been calculated in the LS-coupling scheme. The wave functions used in this work have been calculated by the multiconfiguration Hartree–Fock method. Two sets of wave functions were generated; the larger set consists of 15 configurations for the 1S0 state and 21 for the 1D2 state, and the smaller set consists of seven (1S0) and nine (1D2) configurations. The resulting value of 1.22 s−1 agrees well with the previous calculations of recent years, and is also in essential agreement with experimental measurement.

Radiative decay of the 2p21D2state of beryllium-like iron

The authors have used configuration interaction wavefunctions to calculate wavelengths, line strengths, transition probabilities and lifetimes for transitions from the 2p2 1D2 state of beryllium-like iron. It is found that the 2p2 1D2 level decays to the 2s2p 3P20 level instead of the expected 2s2p 1P10 level.

ChemInform Abstract: THE TERBIUM CHLORIDE‐ALUMINUM CHLORIDE VAPOR SYSTEM. I. ABSORPTION AND EXCITATION SPECTRA

AbstractDas Absorptionsspektrum des bei erhöhten Temp. gemäß Gleichgewicht Agebildeten flüchtigen Komplexes wird im Bereich 20 000‐50 000 cm‐1 gemessen.

The terbium chloride–aluminum chloride vapor system. I. Absorption and excitation spectra

The absorption spectrum of the vapor complex formed at elevated temperatures between TbCl3 and AlCl3 has been measured in the region 20 000–50 000 cm−1. Oscillator strengths of f–f absorption bands below 37 000 cm−1 were determined. Strong absorption due to opposite parity 4f75d states was observed in the 37 000 to 50 000 cm−1 region with a peak molar absorptivity of approximately 500 ℓ/mol cm. Significant additional absorption attributed to a molecular complex was also observed in this region. By measuring the excitation spectrum it was found that the molecular absorption does not appear to lead to fluorescence of the 5D4 state. In contrast, absorption by the 4f75d states does result in strong 5D4 fluorescence.

Nuclear-quadrupole optical hole burning in the stoichiometric material EuP_5O_14

Hole burning, which is attributed to optical pumping of nuclear-quadrupole levels, has been observed in the stoichiometric rare-earth compound, EuP5O14 . The long lifetime of these holes (-60 min) implies slow nuclear-spin flip-flop rates. The small magnetic moment of Eu3+ has prevented conventional magnetic-resonance measurements on Eu3+ compounds, but hole burning provides a sensitive method for the optical detection of nuclear-magnetic resonance and nuclear-quadrupole resonance. We have used hole burning and optically detected nuclear-quadrupole resonance to determine quadrupole splittings in the ground (7Fo) and excited (5Do) states.

Time-resolved fluorescence spectroscopy of two-photon-excited singlet states of mercury

The authors report on the two-photon excitation of 1S0 and 1D2 states in mercury by pulsed ultraviolet dye laser radiation. A time-resolved registration of two-photon-excited fluorescence provided an accurate determination of the radiative lifetimes of the levels 71S0 to 91S0 and 61D2 to 81D2. In an external magnetic field Zeeman quantum beats and the zero-field level crossing signal have been observed. Furthermore the authors describe conditions which cause strong emission of amplified spontaneous radiation in transitions between highly excited mercury levels.

Transition probabilities of europium(III) in zirconium and beryllium fluoride glasses, phosphate glass, and pentaphosphate crystals

Eigenvectors of Eu 3+ were obtained by a least-squares fitting procedure to the measured transitions from the two lowest J levels to a multitude of excited levels up to 41 000 cm −1. The Judd-Ofelt parameters Ω t(t = 2, 4, 6) were obtained by comparison between the U (t) calculated from the eigenvectors, and the observed oscillator strengths. Radiative transition probabilities and branching ratios were evaluated for the excited states 5D J(J = 0, 1, 2, 3) and 5L 6 to 7F J . The agreement between the calculated and observed lifetimes and branching ratios is better in oxide glasses than in the pentaphosphate crystal and fluoride glasses. This can be understood on the basis of the higher variety of sites and hence, better averaging.

The influence of the 4d bandwidth on the M4,5N4,5N4,5Auger spectra of Ag and MgAg

High-resolution photoelectron spectroscopy measurements show that the 4d band is narrower in MgAg (2.0 eV) than in pure Ag (3.6 eV). These results are combined with measurements of the binding energy of the initial states and recent theoretical work to explain differences which have been observed between the M4,5N4,5N4,5 Auger spectra of Ag and MgAg. In MgAg all final-state components of the M4,5N4,5N4,5 transitions are too tightly bound to decay by delocalisation of the (4d2) states, the spectrum is quasiatomic and is in good agreement with atomic structure calculations. In the Ag Auger spectrum, only the 1S0, 1G4, 1D2 and 3P states have a quasiatomic character. The 3F4 and, to a lesser extent, the 3F2,3 components of the Ag spectrum are shown to be degenerate with delocalised (4d,4d) two-hole states and it is suggested that the rapid delocalisation of these components explains the apparent reduction in intensity of the M5N4,5N4,5:3F4 and M4N4,5N4,5:3F2,3 components of the Ag spectrum. A broad 'band-like' feature to the high-energy side of the M4,5N4,5N4,5 spectrum is reduced in the MgAg spectrum to 0.6+or-0.1 of its intensity in the Ag spectrum. This reduction is attributed to the narrower 4d band in MgAg.

Pp scattering in lD2 state

pp scattering in the 1D2 state is investigated in a multichannel N/D formalism with pp → pp, pp → NΔ, and NΔ → NΔ as the coupled channels. The driving force is calculated in the OPE and OBE approximations. The resulting 1D2 amplitude has the standard resonance-like features but has no complex pole corresponding to a diproton resonance.

Single-charge transfer reactions of the ground and metastable states of Xe2+at 300K

Measurements are reported of the reactions of the ground (3P) and metastable electronically excited (1D2 and 1S0) states of Xe2+ ions with several atoms (Ar and Xe) and molecules (H2, N2, O2 and CO2) at 300K. The data were obtained using a selected-ion-flow-tube (SIFT) apparatus. State selection was achieved by introducing suitable 'chemical-filter' gases into the flow tube. The rate coefficients for the reactions with the molecules were large with the exception of some of the reactions of the 1S0 state. Conversely, the atom reactions were generally slow except for the 3P state reaction with Ar in which a favourable pseudo-energy resonance must occur. All the molecular reactions proceeded via single-charge transfer and in the 1D2 reactions with molecules, dissociation of the product ion was usually observed.

Solvent dependence of the 5D3→5D4 transition of Tb3+ in POCl3:SnCl4

Light excitation of Tb3+ in POCl3:SnCl4 at 368±1 and 353±1 nm leads to fluorescence emission arising from both the 5D3 and the 5D4 states of Tb3+, respectively. The 5D4 state is populated via the 5D3 state exclusively, by means of the 5D3→5D4 transition. The appropriate transition probability depends upon adjacent Tb3+ ions in their ground state (self-quenching, kq) and upon interactions between the 5D3 state and the solvent (ks). The ratio of the intensities of the fluorescence emission arising from the 5D3 and 5D4 states, monitored at 437±1 nm (5D3→7F4), 491±1 nm (5D4 →7F6) and 545±1 nm (5D4→7F5), respectively, varies linearly with [Tb3+]. Such fluorescence intensity ratios were employed to determine kq/ks and subsequently to obtain the value of ks. At room temperature ks is equal to 630±10 sec−1. The depopulation process of the 5D4 state of Tb3+ is independent of the solvent.

Crystal structure and fluorescence spectrum of 3Y2O3, WO3: Eu3+

A structural study of the rhombohedral compound 3Y2O3, WO3 doped with Europium was carried out. The fluorescence spectrum of Eu3+ was measured in the frequency range 12500–25000 cm−1. Transitions from the excited state 5D0 to the Stark components of the five lowest 7FJ (J=0,1,2,3,4) states were observed. The analysis revealed that the rare earth ion is within a crystal field of C1 symmetry. We found values for the Bkq parameters which give a good agreement between the observed and calculated levels.

Reactions of 125I Activated by 125Xe(EC)125I Process with Methane

Abstract The reactions of 125I obtained from the 125Xe(EC)125I process with methane have been investigated. It was confirmed that electron scavengers, such as I2, SF6, and O2, play an important role. The main product is only CH3125I, the yield decreasing significantly with the concentration of Xe. By adding various additives, the yield of CH3125I in the presence of trace amount of I2 was assigned as follows: 8.7±6.7% by the hot atom reaction, 35.8±8.0% by 125I+ in the 1D2 state, and 31.5±2.0% by 125I+ in the 3P states. The results are discussed in comparison with those reported on similar reactions utilizing different activation processes. Chemical sequences of the formation of CH3125I are proposed.

Direct measurements of excited-state lifetimes in Mg, Ca, and Sr†

The lifetimes of the lowest 3S1 states in Mg, Ca, and Sr have been measured. In addition, the lifetimes of a number of excited 1S0 and 1D2 states in Ca have been determined, as well as the lifetime of the 4s4p1P1 state of Ca. The measurements were made by observing the exponential decay of the intensity of the fluorescence emitted from excited states selectively populated by one- and two-step dye-laser excitation. The values obtained for the 3S1 lifetimes were τ(Mg) = (9.7 ± 0.5) ns, τ(Ca) = (11.7 ± 0.6) ns, and τ(Sr) = (12.9 ± 0.7) ns.

FURTHER EXAMPLES OF A LIGAND FIELD CALCULATION FOR THE SIXFOLD COORDINATED COMPLEX Fe(H2O)2+6

FURTHER EXAMPLES OF A LIGAND FIELD CALCULATION FOR THE SIXFOLD COORDINATED COMPLEX Fe(H₂O)²⁺₆

Laser-induced fluorescence of metastable xenon ions

Xenon ions in the metastable state 5d 4D 7 2 are excited by means of a tunable dye laser at 6051 Å. The excitation is monitored by non-resonant fluorescence at 5292 Å.

Role of the 4f55d band in the radiationless 5D1→5D coupling in BaCl2:Sm2+ and BaBr2:Sm2+

In this paper, the adiabatic relaxation theory is applied to investigate the origin of rare-earth fluorescence quenching involving multiphonon transitions. The energy level schemes for BaCl2:Sm2+ and BaBr2:Sm2+ have been obtained from the observed fluorescence spectra. The phonon cutoff frequencies, 210 and 140 cm−1 for BaCl2 and BaBr2, respectively, have been determined from vibronic sidebands. From the observed temperature dependence of the fluorescence intensities and lifetimes, it is shown that the 5D1 and 5D0 levels are thermally quenched through radiationless excitation to the 4f55d band and that the population of the 5D0 level from 5D1 involves the 4f55d band as an intermediary. This indirect f (→d) →f relaxation mechanism appears to have resulted from the proximity and relatively large displacement between the adiabatical surfaces of the low-lying 4f55d and the 5D1 states of Sm2+ in BaCl2 and BaBr2.

Selective excitation and decay of the fluorescence emission arising from the 5D4 state of Tb3+ in POCl3:SnCl4

Light excitation of Tb3+ in POCl3:SnCl4 at 488±1 nm giving rise to direct population of the 5D4 state, is accompanied by fluorescence emission whose decay is a simple exponential. On the other hand, indirect population of the 5D4 state, via excitation with shorter wavelengths and relaxation of higher excited states of Tb3+, gives rise to fluorescence emission characterized by a very complex decay law. The nature of the complex decay and the conditions at which maximum fluorescence intensities are attained are discussed. The fluorescence lifetime of the 5D4 state, τ4, is independent of [Tb3+] but decreases slightly at higher temperatures. This is attributed to a temperature dependent quenching process of the 5D4 state of Tb3+ by the solvent.