scholarly journals Ê-μ-V Correlation In One-Colour Photolysis/Ionization Of Tert-Butyl Nitrite

1990 ◽  
Vol 10 (3) ◽  
pp. 197-206 ◽  
Author(s):  
P. Marcus ◽  
I. Platzner ◽  
I. Bar ◽  
S. Rosenwaks
Keyword(s):  
Transition Dipole Moment ◽  
Laser Polarization ◽  
Experimental Conditions ◽  
Transition Dipole ◽  
Vector Correlation ◽  
Peak Splitting ◽  
Tert Butyl ◽  
Spatial Velocity ◽  
Fragment Peak ◽  
532 Nm

An anisotropic spatial velocity distribution was observed for NO+ produced following one-color photolysis/ionization of tert-butyl nitrite (TBN) by a pulsed polarized laser at 266, 355 and 532 nm in a time-of-flight mass spectrometer. The dependence of the NO+ fragment mass peak profile on the wavelength and on the polarization was monitored. The most striking feature is the varying fragment peak splitting obtained under the same experimental conditions by changing the laser polarization direction. This phenomenon is a result of the vector correlation between the laser polarization,Ê, at a given wavelength, the electronic transition dipole moment of TBN,μ, and the direction of the NO fragment velocity, v. The dynamics of the photodissociation process and, in particular, its directional properties are discussed in view of these results.

Two-Dimensional Near-Infrared and Shortwave Infrared Molecular Aggregates: Taking Kasha’s Model to the Next Dimension

2019 ◽  
Author(s):  
Arundhati Deshmukh ◽  
Danielle Koppel ◽  
Chern Chuang ◽  
Danielle Cadena ◽  
Jianshu Cao ◽  
...  
Keyword(s):  
Near Infrared ◽  
Photophysical Properties ◽  
Satellite Telemetry ◽  
Transition Dipole Moment ◽  
Short Wave ◽  
Tissue Imaging ◽  
Transition Dipole ◽  
Deep Tissue Imaging ◽  
Excitonic States ◽  
Shortwave Infrared

Technologies which utilize near-infrared (700 – 1000 nm) and short-wave infrared (1000 – 2000 nm) electromagnetic radiation have applications in deep-tissue imaging, telecommunications and satellite telemetry due to low scattering and decreased background signal in this spectral region. However, there are few molecular species, which absorb efficiently beyond 1000 nm. Transition dipole moment coupling (e.g. J-aggregation) allows for redshifted excitonic states and provides a pathway to highly absorptive electronic states in the infrared. We present aggregates of two cyanine dyes whose absorption peaks redshift dramatically upon aggregation in water from ~ 800 nm to 1000 nm and 1050 nm with sheet-like morphologies and high molar absorptivities (e ~ 10<sup>5 </sup>M<sup>-1</sup>cm<sup>-1</sup>). To describe this phenomenology, we extend Kasha’s model for J- and H-aggregation to describe the excitonic states of <i> 2-dimensional aggregates</i> whose slip is controlled by steric hindrance in the assembled structure. A consequence of the increased dimensionality is the phenomenon of an <i>intermediate </i>“I-aggregate”, one which redshifts yet displays spectral signatures of band-edge dark states akin to an H-aggregate. We distinguish between H-, I- and J-aggregates by showing the relative position of the bright (absorptive) state within the density of states using temperature dependent spectroscopy. Our results can be used to better design chromophores with predictable and tunable aggregation with new photophysical properties.

Theoretical studies on the one- and two-photon absorption of tetrabenzoporphyrins and phthalocyanines

2004 ◽  
Vol 82 (1) ◽  
pp. 19-26 ◽  
Author(s):  
Xin Zhou ◽  
Ai-Min Ren ◽  
Ji-Kang Feng ◽  
Xiao-Juan Liu
Keyword(s):  
Dipole Moment ◽  
Cross Sections ◽  
Density Functional ◽  
Transition Dipole Moment ◽  
Photon Absorption ◽  
Transition Dipole ◽  
Two Photon Absorption ◽  
Two Photon ◽  
Order Of Magnitude ◽  
The One

The one-photon absorption (OPA) properties of tetrabenzoporphyrins (TBPs) and phthalocyanines (Pcs) were studied using the semiempirical ZINDO method and time-dependent density functional theory (TDDFT), respectively. The compared results confirmed that the semiempirical ZINDO method was reasonably reliable when calculating the OPA of tetrabenzoporphyrins and phthalocyanines. On the basis of the OPA properties obtained from the ZINDO method, two-photon absorption (TPA) properties of two series of molecules were investigated, using ZINDO and sum-over-states (SOS) methods. The results showed that the TPA cross-sections of all molecules were in the range of 220.6 × 10–50 – 345.9 × 10–50 cm4·s·photon–1, which were in the same order of magnitude as the values reported in the literature. The relatively larger δ(ω) value for Pcs with respect to that for corresponding TBPs originates from larger intramolecular charge transfer, which can be characterized by the difference of dipole moment between S0 and S1 and the transition dipole moment between S1 and S5.Key words: two-photon absorption, ZINDO, sum-over-states, tetrabenzoporphyrin, phthalocyanines.

scholarly journals Carotenoid-Chlorophyll Interactions in a Photosynthetic Antenna Protein: A Supramolecular QM/MM Approach

Molecules ◽  
2018 ◽  
Vol 23 (10) ◽  
pp. 2589 ◽  
Author(s):  
Matthew Guberman-Pfeffer ◽  
José Gascón
Keyword(s):  
Chlorophyll A ◽  
Protein A ◽  
Transition Dipole Moment ◽  
Protein Domain ◽  
Electronic Coupling ◽  
Stoichiometric Ratio ◽  
Wild Type ◽  
Transition Dipole ◽  
Energy Capture ◽  
Photosynthetic Antenna

Multichromophoric interactions control the initial events of energy capture and transfer in the light harvesting peridinin-chlorophyll a protein (PCP) from marine algae dinoflagellates. Due to the van der Waals association of the carotenoid peridinin (Per) with chlorophyll a in a unique 4:1 stoichiometric ratio, supramolecular quantum mechanical/molecular mechanical (QM/MM) calculations are essential to accurately describe structure, spectroscopy, and electronic coupling. We show that, by enabling inter-chromophore electronic coupling, substantial effects arise in the nature of the transition dipole moment and the absorption spectrum. We further hypothesize that inter-protein domain Per-Per interactions are not negligible, and are needed to explain the experimental reconstruction features of the spectrum in wild-type PCP.

Lifetimes and transition dipole moment functions of NaK low lying singlet states: Empirical and ab initio approach

1998 ◽  
Vol 109 (16) ◽  
pp. 6725-6735 ◽  
Author(s):  
M. Tamanis ◽  
M. Auzinsh ◽  
I. Klincare ◽  
O. Nikolayeva ◽  
R. Ferber ◽  
...  
Keyword(s):  
Dipole Moment ◽  
Ab Initio ◽  
Transition Dipole Moment ◽  
Transition Dipole ◽  
Singlet States ◽  
Moment Functions ◽  
Ab Initio Approach

Fundamental Absorption Band of HD

1974 ◽  
Vol 52 (17) ◽  
pp. 1669-1671 ◽  
Author(s):  
J. Bejar ◽  
H. P. Gush
Keyword(s):  
Dipole Moment ◽  
Absorption Band ◽  
Line Width ◽  
Doppler Effect ◽  
Transition Dipole Moment ◽  
Vibration Band ◽  
Transition Dipole ◽  
Fundamental Absorption Band ◽  
The Doppler Effect

The fundamental rotation–vibration band of HD has been resolved in the gas at 1 atm pressure. The line width appears to be totally due to the Doppler effect and equals 0.026 cm−1. The transition dipole moment has been calculated from the intensities of lines in the R branch: it is found to vary from 4 × 10−5 D for J = 0 to 7 × 10−5 for J = 4.

THEORETICAL STUDY ON PHOTOINDUCED INTRAMOLECULAR CHARGE TRANSFER IN A NOVEL ORGANIC SENSITIZER C201

2011 ◽  
Vol 10 (05) ◽  
pp. 641-649 ◽  
Author(s):  
FENGJIE ZHOU ◽  
YAPING ZHANG ◽  
SHUO CAO ◽  
YONG DING ◽  
SHASHA LIU
Keyword(s):  
Charge Transfer ◽  
Molecular Orbital ◽  
Density Functional ◽  
Intramolecular Charge Transfer ◽  
Transition Density ◽  
Dft Method ◽  
Transition Dipole Moment ◽  
Transition Dipole ◽  
Level Densities ◽  
Charge Difference Density

A new organic dye (C201) composed of triarylamine unit as electron donor and anchoring unit as electron acceptor, was theoretically investigated by quantum chemical methods. We optimized the geometry of C201 with density functional theory (DFT) at B3LYP/6-311G (d) level. Densities of highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO), as well as the energies are listed. The excited states of the dye molecules C201 were calculated by time dependent-DFT (TD-DFT) method. Two main visible bands at 572 nm and 407 nm were mainly attributed to the electronic transition from HOMO→LUMO and HOMO-1→LUMO, respectively. 3D cube representations including transition density (TD) and charge difference density (CDD) directly visualized the character of intramolecular charge transfer of C201. The orientation and strength of transition dipole moment were showed visually using TD. Furthermore, we illustrate the orientation and results of the intramolecular charge transfer by CDD.

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