Effective Masses of Quasifree Electrons in Inert Gas Solids

1974 ◽  
Vol 52 (20) ◽  
pp. 2062-2064
Author(s):  
R. G. Brown ◽  
H. T. Davis
Keyword(s):  
Excited State ◽  
Liquid Helium ◽  
Potential Barrier ◽  
Ground State ◽  
A Priori ◽  
Electronic Energy ◽  
Inert Gases ◽  
Inert Gas ◽  
Effective Masses ◽  
Ground State Energies

The Wigner–Seitz model for a core–core cutoff pseudopotential introduced by Springett et al. is used to predict effective masses of quasifree electrons in inert gas solids. The model has been useful in predicting or correlating ground state energies of electrons in liquid (Springett et al., Raz and Jortner, and Miyakawa and Dexter) and solid (Raz and Jortner) inert gases. The theoretical effective masses reported herein are at least a factor of two too high, even for Ne for which the model gives a good a priori prediction for the ground state quasifree electronic energy. The failure of the model in predicting excited state properties (namely, the effective masses) brings into question Miyakawa and Dexter's use of the potential barrier (Springett el al.) predicted by the same model in treating photoexcitation of electronic bubbles in liquid helium.

Excited-State Dynamics in the RNA Nucleotide Uridine 5’-Monophosphate Investigated by Femtosecond Broadband Transient Absorption Spectroscopy

2019 ◽  
Author(s):  
Matthew M. Brister ◽  
Carlos Crespo-Hernández
Keyword(s):  
Excited State ◽  
Excited States ◽  
Ground State ◽  
Transient Absorption ◽  
Electronic Energy ◽  
Transient Absorption Spectroscopy ◽  
Electronic Relaxation ◽  
Vibrationally Excited ◽  
Excited State Dynamics ◽  
Π State

<p></p><p> Damage to RNA from ultraviolet radiation induce chemical modifications to the nucleobases. Unraveling the excited states involved in these reactions is essential, but investigations aimed at understanding the electronic-energy relaxation pathways of the RNA nucleotide uridine 5’-monophosphate (UMP) have not received enough attention. In this Letter, the excited-state dynamics of UMP is investigated in aqueous solution. Excitation at 267 nm results in a trifurcation event that leads to the simultaneous population of the vibrationally-excited ground state, a longlived <sup>1</sup>n<sub>O</sub>π* state, and a receiver triplet state within 200 fs. The receiver state internally convert to the long-lived <sup>3</sup>ππ* state in an ultrafast time scale. The results elucidate the electronic relaxation pathways and clarify earlier transient absorption experiments performed for uracil derivatives in solution. This mechanistic information is important because long-lived nπ* and ππ* excited states of both singlet and triplet multiplicities are thought to lead to the formation of harmful photoproducts.</p><p></p>

Collisional deactivation of singlet methylene in the photolysis of ketene

1969 ◽  
Vol 47 (18) ◽  
pp. 3345-3353 ◽  
Author(s):  
R. A. Cox ◽  
K. F. Preston
Keyword(s):  
Carbon Monoxide ◽  
Quantum Yield ◽  
Ground State ◽  
Inert Gases ◽  
Inert Gas ◽  
Quantum Yields ◽  
Electronic Relaxation ◽  
Excited Singlet ◽  
State Formula ◽  
Singlet Methylene

An investigation has been made into the effect of inert gas additions on product quantum yields for the photolysis at 2800 and 2490 Å of mixtures of ketene and oxygen and for the photolysis at 2800 Å of mixtures of ketene and carbon monoxide. Concentration ratios of O2 (or CO) to CH2CO were chosen so that the reaction of CH2(3Σg−) with CH2CO could be ignored and C2H4 formation could be attributed entirely to the reaction[Formula: see text]Quenching of the C2H4 quantum yield by inert gases was interpreted in terms of collisional deactivation of CH2(1A1) to the ground state[Formula: see text]and rate constant ratios k2/k1 have been determined for a number of gases: He (0.018), Ar (0.014), Kr (0.033), Xe (0.074), N2 (0.052), N2O (0.10), CF4 (0.047), C2F6 (0.11), and SF6 (0.045). It has been assumed that collision-induced intersystem crossover in excited singlet ketene makes an insignificant contribution to the observed quenching effects, but it has not been possible to verify this assumption experimentally. The mechanism of collision-induced electronic relaxation of singlet methylene is discussed in the light of the results.

The Ultraviolet Absorption Spectrum of Furazan

1972 ◽  
Vol 50 (13) ◽  
pp. 2088-2091 ◽  
Author(s):  
B. J. Forrest ◽  
A. W. Richardson
Keyword(s):  
Absorption Spectrum ◽  
Excited State ◽  
Potential Barrier ◽  
Ground State ◽  
Ultraviolet Absorption ◽  
Ultraviolet Absorption Spectrum

The ultraviolet absorption spectrum of furazan (1,2,5-oxadiazole) in the region 2500–2300 Å has been recorded and analyzed as a π→π* transition from the planar ground state to a non-planar excited state having a potential barrier to planarity of about 215 cm−1.

Excited-State Dynamics in the RNA Nucleotide Uridine 5’-Monophosphate Investigated by Femtosecond Broadband Transient Absorption Spectroscopy

2019 ◽  
Author(s):  
Matthew M. Brister ◽  
Carlos Crespo-Hernández
Keyword(s):  
Excited State ◽  
Excited States ◽  
Ground State ◽  
Transient Absorption ◽  
Electronic Energy ◽  
Transient Absorption Spectroscopy ◽  
Electronic Relaxation ◽  
Vibrationally Excited ◽  
Excited State Dynamics ◽  
Π State

<p></p><p> Damage to RNA from ultraviolet radiation induce chemical modifications to the nucleobases. Unraveling the excited states involved in these reactions is essential, but investigations aimed at understanding the electronic-energy relaxation pathways of the RNA nucleotide uridine 5’-monophosphate (UMP) have not received enough attention. In this Letter, the excited-state dynamics of UMP is investigated in aqueous solution. Excitation at 267 nm results in a trifurcation event that leads to the simultaneous population of the vibrationally-excited ground state, a longlived <sup>1</sup>n<sub>O</sub>π* state, and a receiver triplet state within 200 fs. The receiver state internally convert to the long-lived <sup>3</sup>ππ* state in an ultrafast time scale. The results elucidate the electronic relaxation pathways and clarify earlier transient absorption experiments performed for uracil derivatives in solution. This mechanistic information is important because long-lived nπ* and ππ* excited states of both singlet and triplet multiplicities are thought to lead to the formation of harmful photoproducts.</p><p></p>

Lower bound energy calculations for

1966 ◽  
Vol 62 (4) ◽  
pp. 769-776 ◽  
Author(s):  
Mary Walmsley ◽  
C. A. Coulson
Keyword(s):  
Excited State ◽  
Lower Bound ◽  
Lower Bounds ◽  
Ground State ◽  
Nuclear Charge ◽  
Electronic Energy ◽  
Energy Calculations ◽  
First Excited State

AbstractTwo different calculations are made of lower bounds for the electronic energy of . In the first the method of truncated Hamiltonians due to Bazley and Fox is adapted in such a way that the nuclear charge rather than the energy becomes the eigenvalue. Lower bounds are calculated for the energies of the six lowest σg and six lowest σu states, as well as of the three lowest of both πg and πu symmetries. This approach gives better convergence than when the energy is used as eigenvalue. In the second calculation the method of Temple and Kato is shown to give a satisfactory value for the energy of the ground state, provided that some necessary knowledge of the energy of the first-excited state is available.

AN EMISSION SPECTRUM OF THE DIACETYLENE ION: A STUDY OF SCHÜLER'S "T" SPECTRUM UNDER HIGH RESOLUTION

1956 ◽  
Vol 34 (10) ◽  
pp. 1046-1074 ◽  
Author(s):  
J. H. Callomon
Keyword(s):  
Excited State ◽  
High Resolution ◽  
Emission Spectrum ◽  
Organic Compounds ◽  
Ground State ◽  
Inert Gas ◽  
Vibrational Assignments ◽  
First Excited State ◽  
Helium Discharge ◽  
Very High

Schüler and Reinebeck have described a new spectrum which was observed in a discharge through a mixture of an inert gas and the vapor of any of a number of organic compounds. This spectrum was labelled "T". Further experiments by the authors provided evidence that the carrier of the "T" spectrum was the diacetylene molecule. The "T" spectrum has now been reinvestigated using both normal and fully deuterated diacetylenes in a helium discharge and photographed on grating instruments with very high resolving powers. Previous vibrational assignments were extended, and the rotational structure was completely analyzed in four bands. The results, together with other evidence, show that the carrier of the "T" spectrum is the diacetylene ion, C4H2+. The vibrational and rotational constants differ but little from those of the diacetylene ground state. The spectrum involves a transition between the first excited state A2Πu(i) and the ground state X2Πg(i) of the ion and is analogous in detail to the well-known Fox, Duffendack, and Barker system of CO2+.

Renilla Bioluminescence: A Morphologic Approach to the Location of Photocytes

1974 ◽  
Vol 32 ◽  
pp. 208-209
Author(s):  
Ben O. Spurlock ◽  
Milton J. Cormier
Keyword(s):  
Excited State ◽  
Ground State ◽  
Molecular Basis ◽  
Light Emission ◽  
Chemical Basis ◽  
Electronic Excited State ◽  
Colonial Form ◽  
The Common ◽  
Eighteenth And Nineteenth Centuries ◽  
Catalyzed Oxidation

The phenomenon of bioluminescence has fascinated layman and scientist alike for many centuries. During the eighteenth and nineteenth centuries a number of observations were reported on the physiology of bioluminescence in Renilla, the common sea pansy. More recently biochemists have directed their attention to the molecular basis of luminosity in this colonial form. These studies have centered primarily on defining the chemical basis for bioluminescence and its control. It is now established that bioluminescence in Renilla arises due to the luciferase-catalyzed oxidation of luciferin. This results in the creation of a product (oxyluciferin) in an electronic excited state. The transition of oxyluciferin from its excited state to the ground state leads to light emission.

Ground State and Excited State H-Atom Temperatures in a Microwave Plasma Diamond Deposition Reactor

1996 ◽  
Vol 6 (9) ◽  
pp. 1167-1180 ◽  
Author(s):  
A. Gicquel ◽  
M. Chenevier ◽  
Y. Breton ◽  
M. Petiau ◽  
J. P. Booth ◽  
...  
Keyword(s):  
Excited State ◽  
Ground State ◽  
Microwave Plasma ◽  
Diamond Deposition

Spin-Forbidden Excitation Enables Infrared Photoredox Catalysis

2020 ◽  
Author(s):  
Tomislav Rovis ◽  
Benjamin D. Ravetz ◽  
Nicholas E. S. Tay ◽  
Candice Joe ◽  
Melda Sezen-Edmonds ◽  
...  
Keyword(s):  
Excited State ◽  
Ground State ◽  
Intersystem Crossing ◽  
Photoredox Catalysis ◽  
Infrared Irradiation ◽  
Triplet Excitation ◽  
New Family ◽  
Ir Light

We describe a new family of catalysts that undergo direct ground state singlet to excited state triplet excitation with IR light, leading to photoredox catalysis without the energy waste associated with intersystem crossing. The finding allows a mole scale reaction in batch using infrared irradiation.

Mechanistic analysis of light-driven overcrowded alkene-based molecular motors by multiscale molecular simulations

2021 ◽  
Vol 23 (14) ◽  
pp. 8525-8540
Author(s):  
Mudong Feng ◽  
Michael K. Gilson
Keyword(s):  
Molecular Dynamics ◽  
Excited State ◽  
Molecular Dynamics Simulations ◽  
Ground State ◽  
Molecular Motors ◽  
Motor Performance ◽  
Molecular Simulations ◽  
Mechanistic Analysis ◽  
Dynamics Simulations ◽  
Shed Light

Ground-state and excited-state molecular dynamics simulations shed light on the rotation mechanism of small, light-driven molecular motors and predict motor performance. How fast can they rotate; how much torque and power can they generate?

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