scholarly journals The band systems ending on the 1 s σ2 s σ 1 Ʃ g ( 1 X g ) state of H 2 —Part I

1937 â—½  
Vol 160 (903) â—½  
pp. 487-507 â—½  
Keyword(s):  
Ground State â—½  
Principal Quantum Number â—½  
Electronic States â—½  
Ground Level â—½  
Triplet States â—½  
Private Communication â—½  
Singlet States â—½  
Singlet And Triplet States â—½  
State 1 â—½  
Atomic Helium

It is now well established that the electronic states of the band systems of H 2 have a close analogy to those of atomic helium and consist of a set of singlet states and a set of triplet states. There are no known combinations between singlet and triplet states. The ground level of H 2 is the v = 0, K = 0 level of the even state 1 s σ 1 s σ 1 Ʃ g . The possible states with one electron excited to principal quantum number 2 are 1 s σ 2 s σ 1 Ʃ g , 1 s σ 2 p σ 1 Ʃ u , 1 s σ 2 pπ 1 II u , 1 s σ 2 s σ 3 Ʃ g , 1 s σ 2 p σ 3 Ʃ g and 1 s σ 2 pπ 3 II u Of these the only ones which can go down to the ground state are 1 s σ 2 p σ 1 Ʃ u and 1 s σ 2 pπ σ 1 Ʃ u on account of the triplet ↔ singlet and odd ↔ odd and even ↔ even prohibitions. The bands with these transitions are well known and understood both in emission and absorption. A large number of emission band systems which go down to the states 1 s σ 2 p σ 1 Ʃ u and 1 s σ2 pπ σ 1 II u from higher even states have been found and analysed so that we now have quite discovered, and most of those involving the v = 1 level, which he has greatly extended, I am indebted to a private communication from Professor Dieke. Incidentally the success of this method of locating the position of 1 s σ3 pπ 1 II u is to some extent also a confirmation of my identification of 3 1 O as 1 s σ 3 s σ 1 Ʃ g .

Topological Study of the Protonation of Conjugated Compounds in the Ground State and in the First Excited Singlet and Triplet States

1976 â—½  
Vol 103 (1-4) â—½  
pp. 1-14 â—½  
Author(s):  
J. C. Rayez â—½  
O. Chalvet â—½  
J. Joussot-Dubien â—½  
J. Hoarau
Keyword(s):  
Ground State â—½  
Triplet States â—½  
Excited Singlet â—½  
Singlet And Triplet States â—½  
Conjugated Compounds

scholarly journals Exchange Interaction in Complex Bis[(1,3-Dithiole-2-Thione-4,5-Dithiolato)-di-(Carbonyl)-Cyclopentadienyl Iron(II)]

10.1155/2009/243296 â—½  
2009 â—½  
Vol 2009 â—½  
pp. 1-4
Author(s):  
S. V. Vitushkina â—½  
D. V. Ziolkovskiy â—½  
V. A. Starodub â—½  
I. A. Presniakov â—½  
A. V. Sobolev â—½  
...  
Keyword(s):  
Magnetic Susceptibility â—½  
Triplet State â—½  
Temperature Dependence â—½  
Exchange Interaction â—½  
Spin Density â—½  
Wide Temperature Range â—½  
Electronic States â—½  
Dft Method â—½  
Triplet States â—½  
Singlet And Triplet States

The splitting of the quasidegenerate electronic states in dinuclear bis[(1,3-dithiole-2-thione-4,5-dithiolato)-di-(carbonyl)-cyclopentadienyliron (II)] complex with the bridging, S–S coupled, dimerized sulfur-rich dithiolate ligands, [Fe(C5H5)(CO)2(C3S5-C3S5)Fe(C5H5)(CO)2] (I) was found by the means of Mössbauer spectroscopy and by the measurement of the temperature dependence of magnetic susceptibility in a wide temperature range from 2 K to 300 K. The experimental results were confirmed by the calculations of the singlet and triplet states of the complex, as well as of the distribution of spin density within the bounds of the DFT method in the B3LYP/6-31(dp)G basis. In the more stable triplet state, the spin density is significantly delocalized, which is a characteristic of olefindithiolate complexes.

Ab-initio Calculation on Methylnitrenium Ion (CH3NH)+

1974 â—½  
Vol 29 (5) â—½  
pp. 832 â—½  
Author(s):  
R. Gunde â—½  
A. Ažman
Keyword(s):  
Triplet State â—½  
Ab Initio â—½  
Ground State â—½  
Ab Initio Calculation â—½  
Triplet States â—½  
Singlet And Triplet States

Abstract Ab initio calculation were carried out on the singlet and triplet states of the methylnitrenium ion. The triplet state is the ground state for all values of angle at nitrogen.

An analysis of vibronic coupling in the triplet absorption spectrum of pyrazine

10.1139/v93-193 â—½  
1993 â—½  
Vol 71 (10) â—½  
pp. 1537-1547 â—½  
Author(s):  
Gad Fischer
Keyword(s):  
Theoretical Calculations â—½  
Electronic States â—½  
Emission Spectra â—½  
Vibronic Coupling â—½  
Triplet States â—½  
Model Calculations â—½  
Singlet States â—½  
Out Of Plane â—½  
Hot Band â—½  
Triplet Absorption

New measurements of the singlet–triplet [Formula: see text] absorption spectra of pyrazine and pyrazine-d4 at longer pathlengths and higher vapour pressures have been recorded. Particular attention was paid to the hot band region to the red of the electronic origin. The activities of the out-of-plane vibrations, υ4 and υ10a, were identified in sequence bands, and their triplet state vibrational frequencies were determined, 295 (276, -d4) and 254 (194, -d4) cm−1, respectively. Model calculations were undertaken to match the observed singlet and triplet absorption and emission spectra for vibronic coupling induced by (i) υ10a(b1g), and (ii) υ4 and υ5(b2g). The calculations allowed the ordering and the relative energies of the higher lying triplet states to be determined. The 3B2u and 3B1u electronic states are above the ground electronic state by about 3.9 and 4.4 eV, respectively. The ordering is in analogy with the corresponding singlet states but opposite to that predicted by most theoretical calculations.

scholarly journals CNDO/S-CI Calculations of some Carbonyl-containing Organic Luminophores with a Stilbene Subchromophore

1985 â—½  
Vol 40 (8) â—½  
pp. 859-863
Author(s):  
G. Olbrich â—½  
P. Nikolov â—½  
F. Fratev â—½  
O. E. Polansky
Keyword(s):  
Quantum Yield â—½  
Fluorescence Quantum Yield â—½  
Electronic States â—½  
Solvent Polarity â—½  
Energy Separation â—½  
Triplet States â—½  
Organic Luminophores â—½  
Calculated Energy â—½  
Singlet And Triplet States â—½  
Ci Calculations

For a series of carbonyl-containing compounds with a stilbene subchromophore the lowest ten singlet and triplet states have been calculated with the aid of the CNDO/S-CI method. The results were used to rationalize the relative ordering of the lowest-lying S(ππ*), S(ππ*), T(ππ*), and T(ππ*) electronic states. Using the calculated energy separation between the singlet ππ*and nπ* states and between the singlet ππ* and triplet nπ* states the fluorescence ability of the compounds studied is interpreted. The connection between the structure of the compounds and their fluorescence is discussed. It is shown that an increase of the solvent polarity in some cases may lead to an inversion of the singlet nπ* and ππ* levels and to an enhancement of the fluorescence quantum yield.

Conformational analysis and electronic properties of bithiophene and terthiophene in their ground state as well as in their first excited singlet and triplet states

1996 â—½  
Vol 250 (1) â—½  
pp. 31-39 â—½  
Author(s):  
Michel Belletête â—½  
Nicolas Di Césare â—½  
Mario Leclerc â—½  
Gilles Durocher
Keyword(s):  
Conformational Analysis â—½  
Electronic Properties â—½  
Ground State â—½  
Triplet States â—½  
Excited Singlet â—½  
Singlet And Triplet States

scholarly journals The spectrum of H 2 .-The bands ending on 2p 3 II levels

1931 â—½  
Vol 131 (818) â—½  
pp. 658-683 â—½  
Keyword(s):  
Quantum Number â—½  
Principal Quantum Number â—½  
Electronic States â—½  
Excited Electron â—½  
The Other â—½  
Molecular Axis â—½  
Triplet States â—½  
Triplet Level â—½  
Double Character â—½  
Azimuthal Quantum Number

Rather more than a year ago it was announced that the bands which go down to the two 2 p 3 II ab levels had been found, but owing to the inclusion of a considerable number of wrong lines little progress in understanding them has been made until quite recently. The discovery of these bands is important for several reasons, of which we shall mention one at this stage. It proves that a system of triplet states analogous to the states of the orthohelium line spectrum really exists in the spectrum of H 2 and to that extent confirms the view we have taken of the structure of this spectrum. This follows since the singlet 2 p 1 II ab levels have now been firmly identified with the C level of Dieke and Hopfield; the final levels of the present band systems are undoubtedly 2 p II ab levels, and there is no room for any other 2 p II level in the singlet system. The notation here used is that proposed by Mulliken. It has been described by one of us in the 'Transactions of the Faraday Society,’ vol. 25, p. 628. It is assumed that in all the electronic states of H 2 with which these bands are concerned only one electron gets excited, the other being in an s state ( l = 0). Thus the resultant azimuthal quantum number L of the two electrons is equal to that of the azimuthal quantum number l of the excited electron. The magnitude of both these quantities is thus expressed by the letters s (for l = 0), p (for l == 1), d (for l ==2), etc., in such symbols as 2 p 3 II. In addition we have to specify A the resolved part of L about the molecular axis. This is indicated by the symbols Σ for Ʌ = 0, II for Ʌ = 1, Ʌ for Ʌ = 2. etc. The first number, such as 2 in 2 p 3 II ab , indicates the principal quantum number n and the second such as 3 shows that the level is believed to be a triplet level. The suffixes ab distinguish the double character of II, Δ, etc., levels which arise according to whether the value of Ʌ is positive or negative.

Potential energy curves and dipole moment of NF molecule with inner electron correlation

2015 â—½  
Vol 93 (12) â—½  
pp. 1544-1550 â—½  
Author(s):  
Mingjie Wan â—½  
Huafeng Luo â—½  
Chengguo Jin â—½  
Duohui Huang â—½  
Fanhou Wang
Keyword(s):  
Potential Energy â—½  
Excited States â—½  
Correlation Energy â—½  
Dipole Moments â—½  
Electronic States â—½  
Spectroscopic Properties â—½  
Potential Energy Curves â—½  
Basis Set â—½  
Triplet States â—½  
Singlet And Triplet States

The potential energy curves and dipole moments for the low-lying electronic states of the NF molecule are found by using highly accurate multireference configuration interaction plus the Davidson correction with the AV5Z basis set. All 16 electrons are used in the correlation energy calculations, which are used to characterize the spectroscopic properties of a manifold for singlet and triplet states. X3Σ–, a1Δ, b1Σ+, A3Π, 23Σ–, 23Π, 21Δ, 33Σ–, 13Σ+, and 13Δ electronic states correlate with the two lowest dissociation channels N(4Su) + F(2Pu) and N(2Du) + F(2Pu) are investigated. Note that the b1Σ+ state has two depth wells, but only one depth well was observed in the experiment. The spectroscopic parameters (Re, ωe, ωeχe, De, Be, and Te) are derived, which are in excellent agreement with the available experimental data and the other theoretical values. The molecular parameters and dipole moments for the ground and excited states are also obtained.

Thermal and photochemical reactivity of cyclopropene derivatives: a semi-empirical molecular orbital study

10.1139/v77-340 â—½  
1977 â—½  
Vol 55 (13) â—½  
pp. 2482-2491 â—½  
Author(s):  
J. A. Pincock â—½  
R. J. Boyd
Keyword(s):  
Molecular Orbital â—½  
Ground State â—½  
Geometry Optimization â—½  
Triplet States â—½  
Excited Singlet â—½  
Photochemical Reactivity â—½  
Molecular Orbital Study â—½  
Singlet And Triplet States â—½  
Semi Empirical â—½  
Abinitio Calculations

The MINDO/3 semi-empirical MO method has been used to study the conversion of cyclopropene to vinyl carbene. In particular, the surfaces of the ground state and the first excited singlet and triplet states have been calculated. Additional calculations, including geometry optimization, have been carried out on vinyl substituted cyclopropenes. In general, the results are consistent with the known thermal and photochemical reactivities of cyclopropenes and the results of the few abinitio calculations on these species.

Calculation of Population Densities of Helium Atoms in Non-L.T.E. Plasmas

1973 â—½  
Vol 28 (9) â—½  
pp. 1422-1431 â—½  
Author(s):  
H. W. Drawin â—½  
F. Emard â—½  
K. Katsonis
Keyword(s):  
Stationary State â—½  
Inhomogeneous Plasma â—½  
Triplet States â—½  
Helium Atoms â—½  
Plasma State â—½  
Collisional Radiative Model â—½  
Singlet And Triplet States â—½  
Radiative Model â—½  
Atomic Helium â—½  
Good Agreement

Particle densities of helium atoms in the ground and excited states have been calculated for non-L.T.E. plasmas on the basis of a collisional-radiative model in which singlet and triplet states have separately been taken into account. Distinction is made between two physical situations: 1- a homogeneous stationary state, 2- a transient and/or inhomogeneous plasma state. In both cases, the particle densities have been calculated for an optically thin, a slightly optically thick and strongly absorbing plasmas. Only the results for the homogeneous stationary state are presented in this paper. Those for the transient and/or inhomogeneous states have been summarized in numerical tables which will be sent on request. (Title: "Tables of reduced population coefficients for the levels of atomic helium", Report EUR-CEA-FC-697.) The tables are sufficiently complete to permit a wide application in the field of spectroscopic diagnostics of different types of non-L.T.E. plasmas. - Comparison of our results with the values measured by Boersch et al. 10 shows good agreement with our calculations when one assumes that the observed plasma is strongly inhomogeneous and dominated by diffusion.

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