Stereochemical alterations of 2E chromium(III) excited-state behavior in dicyanotetraazacyclotetradecane complexes. Ground-state x-ray crystal structures, photophysical behavior, and molecular mechanics simulations of stereochemical effects

1992 ◽  
Vol 31 (14) ◽  
pp. 3091-3103 ◽  
Author(s):  
Ronald B. Lessard ◽  
Mary Jane Heeg ◽  
Tione Buranda ◽  
Marc W. Perkovic ◽  
Carolyn L. Schwarz ◽  
...  
Keyword(s):  
Excited State ◽  
Molecular Mechanics ◽  
Crystal Structures ◽  
Ground State ◽  
State Behavior ◽  
X Ray ◽  
Photophysical Behavior

scholarly journals Muonic x-ray laser assisted by catalyzed fusion of deuterium and tritium

1987 ◽  
Vol 5 (2) ◽  
pp. 393-398 ◽  
Author(s):  
T. Tajima ◽  
S. Eliezer
Keyword(s):  
Excited State ◽  
Photon Energy ◽  
Ground State ◽  
X Ray

The possibility of an X-ray laser by irradiation of muon beams on a thin rod of deuterium-tritium mixture is discussed. The excited state of dtμ-mesomolecules (J, v) = (1, 0) can be induced to make radiative chain transitions with photon energy of 90 eV to the ground state (0, 0), evacuated by fusion.

Modeling the X-ray emissions from the geo-space environment

2020 ◽  
Author(s):  
Tianran Sun
Keyword(s):  
Solar Wind ◽  
Excited State ◽  
Ground State ◽  
Heavy Ion ◽  
High Charge State ◽  
Space Environment ◽  
Neutral Component ◽  
X Ray ◽  
Working Groups ◽  
Solar Wind Charge Exchange

<p>The Earth's magnetosheath is luminous in the soft X-ray band, due to the solar wind charge exchange (SWCX) process. SWCX occurs when a heavy solar wind ion with a high charge state encounters with a neutral component. The heavy ion obtains an electron and gets into an excited state. It then decays to the ground state and emits a photon in the soft X-ray band. Considering that the X-ray emission from the magnetosheath is higher compared to that from the magnetosphere, information about the boundary positions can be derived from an X-ray image of the magnetosheath.</p><p> </p><p>The solar wind - magnetosphere - ionosphere link explorer (SMILE) is a mission jointly supported by ESA and CAS, which aims at exploring the dynamics in the whole system. Soft X-ray Imager (SXI) is expected to provide X-ray images of the magnetosphere. The Modeling Working Group (MWG) is one of the four working groups of SMILE. Studies about the modeling of X-ray emissions as well as the method to derive the boundary positions are two main topics of the MWG. The main progress of MWG will be summarized here. </p>

Structure of the 70 S ribosome: implications for movement

2002 ◽  
Vol 30 (6) ◽  
pp. 1159-1161 ◽  
Author(s):  
H. F. Noller ◽  
A. Baucom
Keyword(s):  
16S Rrna ◽  
Crystal Structures ◽  
Ground State ◽  
Ribosomal Subunit ◽  
Molecular Machine ◽  
Structural Elements ◽  
X Ray ◽  
Functional States ◽  
Moving Parts

The ribosome is a complex molecular machine, with moving parts, many of which are structural elements of rRNA. We compared the X-ray crystal structures of three different functional states of the 30 S ribosomal subunit - two from crystal structures of the isolated 30 S subunit from the Ramakrishnan group and one from a complex of the 70 S ribosome. Even though all three structures are in what could be called the ‘ground state’ of the subunit, many conformational differences are found, distributed over the whole structure. A striking example is the undulating movement of the penultimate stem of 16S rRNA, which forms several intersubunit bridges with the 50 S subunit.

From vine to wine: photophysics of a pyranoflavylium analog of red wine pyranoanthocyanins

2017 ◽  
Vol 89 (12) ◽  
pp. 1761-1767 ◽  
Author(s):  
Adilson A. Freitas ◽  
Cassio Pacheco Silva ◽  
Gustavo Thalmer M. Silva ◽  
António L. Maçanita ◽  
Frank H. Quina
Keyword(s):  
Excited State ◽  
Ground State ◽  
Red Wine ◽  
Weak Acid ◽  
Acid Form ◽  
Excited Singlet ◽  
Fast Relaxation ◽  
Photophysical Behavior ◽  
Bond Reorganization ◽  
Transfer State

AbstractIn the ground state, the p-methoxyphenyl-substituted pyranoflavylium cation I, prepared by the reaction of the 5,7-dihydroxy-4-methylflavylium cation with p-methoxybenzaldehyde, is a weak acid (pKa=3.7±0.1). In its lowest excited singlet state, I is a moderate photoacid (pKa*=0.67) in 30% methanol-water acidified with trifluoroacetic acid (TFA). In comparison to anthocyanins and 7-hydroxyflavylium cations, the photoacidity of I is much less pronounced and the rate of proton loss from the excited acid form of I much slower (by a factor of up to 100). In 50% ethanol:0.10 mol dm−3 HClO4, the excited state of the acid form of I undergoes fast (12 ps) initial relaxation (potentially in the direction of an intramolecular charge transfer state), followed by much slower (340 ps) adiabatic deprotonation to form the excited base. The excited base in turn exhibits a moderately fast relaxation (70 ps), consistent with solvent hydrogen-bond reorganization times, followed by slower but efficient decay (1240 ps) back to the ground state. As in uncomplexed anthocyanins and 7-hydroxyflavylium cations, the photophysical behavior of I points to excited state proton transfer as the dominant excited state deactivation pathway of pyranoanthocyanins, consistent with relatively good photostability of natural pyranoanthocyanins.

Structural Studies of a Series of Organic Non-Linear Optical Materials

1997 ◽  
Vol 53 (5) ◽  
pp. 812-821 ◽  
Author(s):  
J. C. Cole ◽  
J. M. Cole ◽  
G. H. Cross ◽  
M. Farsari ◽  
J. A. K. Howard ◽  
...  
Keyword(s):  
Crystal Structures ◽  
Ground State ◽  
Optical Materials ◽  
Dipole Moments ◽  
Solvent Polarity ◽  
Structural Studies ◽  
Acta Cryst ◽  
X Ray ◽  
Solution State ◽  
X Ray Crystallography

The crystal structures of {4-[bis(diethylamino)methylium]phenyl}dicyanomethanide (I), {4-[cyano(4-methylpiperidyl)methylium]phenyl } dicyanomethanide (II), {4-[cyano(1-pyrrolidinyl)methylium]phenyl}dicyanomethanide (IV) and (Z)-{4-[1,3-dicyano-3-(diethylamino)-2-propenylium]phenyl} dicyanomethanide have been determined by X-ray crystallography. Together with (Z)-{4-[1-cyano-3-(diethylamino)-2-propenylium]phenyl}dicyanomethanide [(III): Cole, J. C., Howard, J. A. K., Cross, G. H. & Szablewski, M. (1995). Acta Cryst. C51, 715–718], these compounds exhibit varying degrees of quinoidal characteristics and yet have predominantly zwitterionic ground state character. The presence of high dipole moments in the crystal can thus be inferred and are substantiated by measurements of high solution-state dipole moments. Negative solvatochromism (hypsochromism on increasing solvent polarity) confirms the zwitterionic character in at least two of the series.

Sign in / Sign up

Export Citation Format

Share Document