A STUDY OF NUCLEON FORCES WITH REPULSIVE CORES: IV. CALCULATIONS OF THE SHAPE-DEPENDENT PARAMETERS IN NEUTRON–PROTON SCATTERING

1958 ◽  
Vol 36 (5) ◽  
pp. 579-584 ◽  
Author(s):  
R. L. Preston ◽  
M. A. Preston
Keyword(s):  
Phase Shift ◽  
Singlet State ◽  
Scattering Length ◽  
Effective Range ◽  
Repulsive Core ◽  
Triplet States ◽  
Proton Scattering ◽  
Dependent Parameter ◽  
Singlet And Triplet States ◽  
Experimental Values

The magnitudes of the coefficients P and Q in the phase-shift expansion k cot [Formula: see text] have been investigated in the case of repulsive-core NP interactions. For square, Gaussian, exponential, and Yukawa shapes, which fit experimental values of the scattering length and the effective range, the shape-dependent parameter P has been computed as a function of rc in both singlet and triplet states. Also, for square and Yukawa shapes, which fit the scattering length and effective range, Q has been computed in the singlet state.

A STUDY OF NUCLEON FORCES WITH REPULSIVE CORES: III. LOW ENERGY PROPERTIES OF THE LÉVY POTENTIAL

1957 ◽  
Vol 35 (4) ◽  
pp. 451-454 ◽  
Author(s):  
M. A. Preston ◽  
J. Shapiro
Keyword(s):  
Binding Energy ◽  
Singlet State ◽  
Scattering Length ◽  
Low Energy ◽  
Proton Scattering ◽  
Core Radius ◽  
Deuteron Binding Energy ◽  
Coupling Constant ◽  
Spin Dependence ◽  
The Core

An attempt has been made to select the core radius and coupling constant of the Lévy potential for the interaction of two nucleons in order to fit the binding energy of the deuteron and the singlet state neutron–proton scattering length. It was found that these two quantities cannot be fitted simultaneously. For any given choice of coupling constant, a somewhat larger core radius is required to fit the deuteron binding energy than is required for the scattering length. This spin dependence of the core radius does not preclude the possibility of a fit to the low energy data with the Lévy potential.

Molecular orbital studies of the singlet and triplet states of formylmethylene conformers

1991 ◽  
Vol 69 (11) ◽  
pp. 1630-1635 ◽  
Author(s):  
Ratnakar K. Gosavi ◽  
Manuel Torres ◽  
Otto P. Strausz
Keyword(s):  
Singlet State ◽  
Closed Shell ◽  
Basis Set ◽  
Planar Geometry ◽  
Present Calculation ◽  
Triplet States ◽  
Excited Singlet ◽  
Singlet And Triplet States ◽  
Ci Calculations ◽  
Single Configuration

The energies and geometries of the low-lying electronic states of formylmethylene have been calculated at the SCF and CI levels using 6-31G** basis set. In agreement with previous reports and accumulated experimental observations, the ground state is the carbenoid triplet with a planar geometry. Also, in agreement with all previous single configuration SCF and CI calculations, the lowest excited singlet state is computed to be the nonplanar closed shell carbenoid structure. In contrast, accumulated experimental evidence along with previously reported MC–SCF results require this state to be planar. The present calculation predicts the existence of a (σ–σ) 1,3-diradical 1A′ state, which appears to be identical to the MC–SCF lowest singlet state, but this state lies some 11 kcal/mol above the closed shell carbenoid 1A state. Apparently, single configuration SCF methods are inadequate for the correct description of the electronic manifold of formylmethylene. Key words: formylmethylene, singlet and triplet states, ab initio MO calculations, conformers, molecular structure.

Protonation of the Trimethylated Pyrichrominium Ion

1986 ◽  
Vol 41 (4) ◽  
pp. 661-664
Author(s):  
J. Koput ◽  
B. Marciniak ◽  
S. Paszyc
Keyword(s):  
Transfer Reaction ◽  
Energy Levels ◽  
Proton Transfer Reaction ◽  
Oscillator Strengths ◽  
Triplet States ◽  
Excited Singlet ◽  
Triplet Energy ◽  
Charge Densities ◽  
Singlet And Triplet States ◽  
Experimental Values

pKSpectroscopic manifestations of protonation of the trimethylated pyrichrominium ion studied previously experimentally [1] are investigated using a semiempirical INDO/S Cl method. Singlet and triplet energy levels of the free ion and several protonated species are calculated, and transition energies and oscillator strengths are compared with experimental spectra. Calculated charge densities on nitrogen atoms are correlated with experimental values for the ground and lowest excited singlet and triplet states. The possibility of the proton transfer reaction (phototautomerization) in the lowest excited singlet state of monoprotonated species is discussed on the basis of INDO/S Cl calculations, fluorescence and absorption spectroscopy.

Low-lying activated states of chloroiridium phthalocyanine aggregates in glassy solution at low temperatures

1988 ◽  
Vol 66 (1) ◽  
pp. 86-92 ◽  
Author(s):  
W.-H. Chen ◽  
K. E. Rieckhoff ◽  
E.-M. Voigt
Keyword(s):  
Singlet State ◽  
Torsional Oscillation ◽  
Zero Point ◽  
Triplet States ◽  
Excited Singlet ◽  
Glassy Solution ◽  
Ground Singlet State ◽  
Modes Of Vibration ◽  
State Formula ◽  
Singlet And Triplet States

Studies of phosphorescence intensities and lifetimes of two chloroiridium phthalocyanine aggregates in α-chloronaphthalene between 5 and 80 K have revealed the existence of low-lying activated states only a few tens of cm−1 above the zero-point vibration in both lowest singlet and triplet states. From the data, activation energies of intersystem crossings between the two multiplicities associated with these states have been obtained as follows: for crossing from the first excited singlet to the lowest triplet state, Ea = 42 ± 10 and 29 ± 10 cm−1, respectively, for the two aggregates; for crossing from the lowest triplet to the ground singlet state, [Formula: see text] and 23 ± 5 cm−1, respectively. These activated states are tentatively attributed to certain intermolecular modes of vibration in aggregates. Specifically, they fit the model of molecular torsional oscillation of two and three parallel-sheet arrangements. On the basis of these findings, we propose that the first Ea (or [Formula: see text]) is the fundamental librational frequency of the dimer and the second Ea (or [Formula: see text]) is that for the trimer.

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.

Lamb shift in the metastable states of the helium atom

1966 ◽  
Vol 291 (1424) ◽  
pp. 94-105 ◽  
Keyword(s):  
Helium Atom ◽  
Lamb Shift ◽  
Metastable States ◽  
Oscillator Strengths ◽  
Triplet States ◽  
Excitation Energies ◽  
Ionization Energies ◽  
Singlet And Triplet States ◽  
Experimental Values ◽  
Average Excitation Energy

The radiative corrections of order α 3 rydbergs are evaluated for the ionization energy of the metastable states 2 1 , 3 S, of the helium atom. In the calculation of the average excitation energy k 0 , the main contribution comes from the transition to and ( ms, np ) and ( ms, ∊p ) states. The oscillator strengths for transitions to (1 s, ∊p ), (2 s, ∊p ) and (3 s, ∊p ) states are evaluated by using six-parameter wavefunction for the metastable states and a product of a hydrogenic wavefunction with Z = 2 for the s electron and a wavefunction analogous to the Hartree wavefunction for the excited p electron. Making use of these oscillator strengths and a method used by Pekeris, the values of the average excitation energies for the singlet and triplet states are found to be 77.09 ± 1.6 and 79.84 ± 1.0 rydbergs respectively. With these values of the average excitation energies, the Lamb shift corrections, including the estimate of a α 4 Ry order corrections, to the ionization energies of the singlet and triplet states become – 0.106 ± 0.018 cm -1 and –0.129 ± 0.013 cm –1 respectively. When they are added to the theoretical values of the ionization energies obtained by Pekeris, the values of the ionization energies become 32033.212 ± 0.018 an d 38454.698 ± 0.013 cm -1 compared with Herzberg’s experimental values of 32033.24 ± 0.05 an d 38454.73 ± 0.05 cm -1 for the singlet and triplet states respectively.

The photolysis and thermal decomposition of pyruvic acid in the gas phase

1985 ◽  
Vol 63 (2) ◽  
pp. 549-554 ◽  
Author(s):  
S. Yamamoto ◽  
R. A. Back
Keyword(s):  
Thermal Decomposition ◽  
Gas Phase ◽  
Pyruvic Acid ◽  
Light Emission ◽  
Singlet State ◽  
Hydrogen Atom Transfer ◽  
Triplet States ◽  
Primary Process ◽  
Weak Absorption ◽  
Singlet And Triplet States

The photolysis of pyruvic acid vapour has been studied at wavelengths of 366, 345, and 320 nm, at a temperature of 340 K and pressures from about 1 to 10 Torr. Products observed were CO2 and CH3CHO, with the former always in excess, and a quantum yield of CO2 of 0.9 ± 0.1 at 366 nm. Light emission was also observed, and from the effect of added O2 it was concluded that emission occurred from both singlet and triplet states. It is suggested that the primary process in the photolysis is an internal hydrogen-atom transfer followed by dissociation into CO2 and CH3—C—OH, with the latter then rearranging to give CH3CHO and other products.The absorption spectrum is reported; the first system begins at about 380 nm, rising to a maximum at about 350 nm, with εmax = 10 M−1 cm−1, and is attributed to the first excited π* ← n+ singlet state. Weak absorption below 300 nm is probably due to the π* ← n− state and much stronger absorption below 220 nm to the π* ← π state.The thermal decomposition was studied briefly at temperatures from 455 to 584 K and pressures from about 0.8 to 7 Torr. Products were the same as in the photolysis, and Arrhenius parameters of log A (s−1) = 7.19 and E = 27.7 kcal/mol were obtained, based on the formation of CO2, which was apparently a simple, homogeneous unimolecular process.

scholarly journals The Adenine and Thymine Molecules. Some Excited Singlet and Triplet Levels of the Normal and Tautomeric Forms

1977 ◽  
Vol 32 (7-8) ◽  
pp. 647-649 ◽  
Author(s):  
Julio Marañon ◽  
Oscar M. Sorarrain
Keyword(s):  
Relative Stability ◽  
Triplet States ◽  
Excited Singlet ◽  
Tautomeric Forms ◽  
Singlet And Triplet States ◽  
Experimental Values

Abstract The shape of the barrier for the H transfer between the normal and tautomeric forms have been determined for the adenine and thymine molecules. The correlations for several singlet and triplet states has been calculated using the CNDO/2-Cl method. The relative stability between both conformations and the agreement with some experimental values is also discussed.

Photocyclization of 2-vinylbiphenyls: stereochemistry of the triplet state cyclization

1985 ◽  
Vol 63 (8) ◽  
pp. 2192-2196 ◽  
Author(s):  
René Lapouyade ◽  
Claude Manigand ◽  
Aziz Nourmamode
Keyword(s):  
Excited State ◽  
Triplet State ◽  
Trans Isomer ◽  
Singlet State ◽  
Membered Ring ◽  
Quantum Yields ◽  
Triplet States ◽  
Singlet Excited State ◽  
Singlet And Triplet States ◽  
Cis Isomer

The photochemistry of five- to eight-membered ring containing 2-cycloalkenyl biphenyls was examined under direct and sensitized irradiation. From the singlet excited state only trans 9,10-cycloalkyl-9,10-dihydrophenanthrenes were obtained. From the triplet state the trans isomer was exclusively formed from 2-cyclopentenyl and 2-cyclohexenyl biphenyls while the cis isomer also appeared with 2-cycloheptenyl and 2-cyclooctenyl biphenyls. We propose that the cis isomers resulted from the cyclization of the perpendicular triplet of cycloheptenyl biphenyl and from the perpendicular and trans triplet of cyclooctenyl biphenyl. Whereas the photocyclization of 2-vinylbiphenyls was regarded as a singlet-state reaction, the quantum yields of reaction of 2-cycloalkenyl biphenyls, from both singlet and triplet states, were high (ΦS = 0.20–0.26; ΦT = 0.15–0.46).

Formation of a Bound State in the Presence of Repulsive Interaction

2003 ◽  
Vol 17 (18n20) ◽  
pp. 3242-3250 ◽  
Author(s):  
J. D. Fan ◽  
Y. M. Malozovsky
Keyword(s):  
Triplet State ◽  
Multiple Scattering ◽  
Singlet State ◽  
Effective Interaction ◽  
Bound State ◽  
Repulsive Interaction ◽  
Triplet States ◽  
Hartree Potential ◽  
Singlet And Triplet States ◽  
T Matrix

We have examined the effective interaction of two fermions in terms of the T-matrix and shown that there are two different series of ladder diagrams in describing the effective interaction: (1) the exchange ladder diagrams giving rise to the T-matrix for the triplet state with poles for attractive interaction and (2) the Hartree ladder diagrams describing the multiple scattering on the Hartree potential and producing the T-matrix for the singlet state with poles for repulsive interaction. It is verified that a bound state of two fermions in the singlet state exists only in the presence of repulsive interaction between them. We further argue that the potential in the Schrodinger equation should be spin-dependent to describe both the singlet and triplet states.

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