Lifetime of the 5s5p1P1 Level of Strontium

1973 ◽  
Vol 51 (10) ◽  
pp. 1088-1090 ◽  
Author(s):  
L. O. Dickie ◽  
F. M. Kelly ◽  
T. K. Koh ◽  
M. S. Mathur ◽  
F. C. Suk
Keyword(s):  
Oscillator Strength ◽  
Resonance Line ◽  
Excited Singlet ◽  
Singlet Level

The lifetime of the first excited singlet level, 5s5p1P1, of strontium has been measured using the Hanle resonance of the 5s21S0 – 5s5p1P1, 4607 Å, resonance line. The lifetime of the 5s5p1P1 level is 5.29 ± 0.10 ns and the oscillator strength of the 4607 Å line is 1.80 ± 0.03. These results are compared with previous measurements.

Lifetime of the 6s7p1P1 Level of Barium

1971 ◽  
Vol 49 (9) ◽  
pp. 1098-1102 ◽  
Author(s):  
L. O. Dickie ◽  
F. M. Kelly
Keyword(s):  
Oscillator Strength ◽  
Resonance Line ◽  
Excited Singlet

The lifetime of the second excited singlet P level of barium 6s7p1P1 has been determined from the width of the Hanle resonance of the 6s7p1P1–6s21S0 3071.58 Å resonance line. The lifetime is determined to be 13.2 ± 0.4 × 10−9 s. From this lifetime the oscillator strength of the 3072 Å transition is 0.12 ± 0.05 and that of the 6s7p1P1–6s5d1D2 4726 Å is 0.09 ± 0.04.

SELECTIVE REFLECTION FROM MERCURY VAPOR AT HIGH PRESSURES

1957 ◽  
Vol 35 (1) ◽  
pp. 98-113 ◽  
Author(s):  
H. L. Welsh ◽  
J. A. Galt
Keyword(s):  
Oscillator Strength ◽  
Classical Theory ◽  
Resonance Line ◽  
High Pressures ◽  
Mercury Vapor ◽  
Square Root ◽  
Special Design ◽  
Selective Reflection ◽  
Absorbing Medium ◽  
Reflection Maximum

Selective reflection from mercury vapor in the region of the 2537 Å resonance line was investigated at pressures up to 340 atm. using reflection cells of special design. The results were interpreted on the basis of the classical theory of reflection from an absorbing medium. By fitting calculated curves to the experimental reflection contours, values of the oscillator strength, f, and the damping constant, γ, were determined. The f values so obtained are density-dependent and at high pressures are approximately equal to one half the value for the free atom. As predicted by theory, the damping constant varies directly as the density of the atoms in the vapor. This result contradicts the earlier work of Welsh, Kastner, and Lauriston (1950) in which it was concluded that γ varies as the square root of the density. A subsidiary reflection maximum was observed at 2540 Å; it is attributed to Hg2 molecules which occur in relatively large concentrations at high densities. Some preliminary observations on the selective reflection at the 1850 Å resonance line were made up to 4.4 atm.

Lifetime of the 6s6p1P1 level of barium

1970 ◽  
Vol 48 (7) ◽  
pp. 879-883 ◽  
Author(s):  
L. O. Dickie ◽  
F. M. Kelly
Keyword(s):  
Recent Work ◽  
Hollow Cathode ◽  
Atomic Beam ◽  
Resonance Line ◽  
Resonance Radiation ◽  
Zero Field ◽  
Excited Singlet ◽  
Level Crossing ◽  
Hollow Cathode Lamp ◽  
Good Agreement

The lifetime of the first excited singlet P level of barium, 6s6p1P1, has been determined from the width of the zero field level crossing, i.e. the Hanle effect, of the 6s6p1P1 –6s21S0, 5535 Å resonance line. The resonance radiation was produced in a hollow cathode lamp and the scattering atoms by an atomic beam. After taking account of coherence narrowing, the lifetime is determined to be 8.37 ± 0.14 × 10−9 s, in good agreement with other recent work.

Impact of t-butyl group on the singlet–triplet energy gap via weak orbital overlap of [1,2,5]-thiadiazolo[3,4-C] pyridine-based TADF emitters: Structural modification

2018 ◽  
Vol 17 (07) ◽  
pp. 1850048
Author(s):  
Saravanan Chinnusamy ◽  
Nasrin I. Shaikh ◽  
Milind S. Dangate
Keyword(s):  
Oscillator Strength ◽  
Energy Gap ◽  
Singlet State ◽  
Spatial Separation ◽  
Excited Singlet ◽  
Triplet Energy ◽  
Excited Triplet ◽  
Butyl Group ◽  
State Formula ◽  
Homo And Lumo

We theoretically investigated the combination of D-A and D-spacer (phenyl ring)-A with an electron donating alkyl (t-butyl) group. The strategy of twisting the geometry of the molecule with the alkyl substituents exclusion of strong electron-withdrawing or -donating groups leads to gain efficient deep blue-to-blue thermally activated delayed fluorescence (TADF) emitter through maintaining the band gap while the reduction of singlet-triplet energy gap ([Formula: see text]. The t-butyl group strongly twisted the conformation of molecules by the steric hindrance, which resulted in weak highest occupied molecular orbital (HOMO) and lowest occupied molecular orbital (LUMO) overlap ([Formula: see text] and efficient spatial separation of HOMO and LUMO ([Formula: see text] in the [Formula: see text] state. In contrast, designed molecules [Formula: see text] state own large HOMO and LUMO overlap of excited singlet state ([Formula: see text] and inefficient spatial separation of HOMO and LUMO. The computed results indicated that introducing alkyl group into the phenyl ring of the acceptor of the designed molecules cannot affect the [Formula: see text]. The [Formula: see text] is mainly related to the [Formula: see text], which can be adjusted by tuning the orbital [Formula: see text]. The large modular orbital overlap at [Formula: see text] and [Formula: see text] excited states resulted in large [Formula: see text], which occurs in the range of 0.38–0.59[Formula: see text]eV whose dominant contribution switches from charge transfer to local excitation. Our studied results reiterate (10.1038/srep10923) that modular orbital overlap of [Formula: see text], HOMO and LUMO overlap of excited triplet state [Formula: see text], spatial separation of HOMO and LUMO in the excited singlet state ([Formula: see text], and spatial separation of HOMO and LUMO in the excited triplet state ([Formula: see text] are the essential factors to determine [Formula: see text] when inconsistencies between [Formula: see text] and [Formula: see text] exist. Increasing the dihedral angle between [Formula: see text] and [Formula: see text] from molecules 1–4 (9–12) decreases the transition dipole moment, which lowers the oscillator strength. When changing the connection position between [Formula: see text] and [Formula: see text], molecules 5–8, the oscillator strength reduced to half with respect to molecules 1–4 and 9–12. The present work provides a theoretical understanding of the impact of alkyl substituents on the overlap of HOMO–LUMO resulting to tuning the [Formula: see text], as well as its influence on the oscillator strength, which may be a reliable idea to design efficient TADF emitters.

Emission and Deactivation of the Excited States of 2,3-Pentanedione

1972 ◽  
Vol 50 (9) ◽  
pp. 1338-1344 ◽  
Author(s):  
A. W. Jackson ◽  
A. J. Yarwood
Keyword(s):  
Triplet State ◽  
Gas Phase ◽  
Excited States ◽  
Singlet State ◽  
Triplet States ◽  
Excited Singlet ◽  
Vibrationally Excited ◽  
Singlet Level ◽  
Singlet And Triplet States ◽  
Fluorescence And Phosphorescence

Vibrationally excited singlet and triplet states of 2,3-pentanedione are formed by photolysis at 365 nm. The processes removing these excited states in the gas phase are studied by measuring the fluorescence and phosphorescence yields. Fluorescence can occur from the vibrationally excited, as well as the vibrationally equilibrated, singlet state. The fluorescence and phosphorescence data are considered in terms of mechanisms which involve either weak or strong collisions. Although the data cannot distinguish between the alternatives, there are two significant conclusions. The fluorescence data require that emission occur from at least two levels in the singlet manifold. To explain the phosphorescence data, the highest emitting singlet level must not lead to a vibrationally equilibrated triplet state.

The Metastability of the Lowest Excited Singlet Level of Naphthalene

1949 ◽  
Vol 17 (6) ◽  
pp. 516-520 ◽  
Author(s):  
M. Kasha ◽  
R. V. Nauman
Keyword(s):  
Excited Singlet ◽  
Singlet Level

scholarly journals An astrophysical oscillator strength for the S II 94.7-nm resonance line and S abundances in DLAs

2001 ◽  
Vol 325 (2) ◽  
pp. 767-771 ◽  
Author(s):  
P. Bonifacio ◽  
E. Caffau ◽  
M. Centurion ◽  
P. Molaro ◽  
G. Vladilo
Keyword(s):  
Oscillator Strength ◽  
Resonance Line
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