Stability of Excited Exciton States in Semiconductor Quantum Dots Under a Lateral Electric Field

2021 ◽  
Author(s):  
S. A. Safwan ◽  
Nagwa El Meshad
Keyword(s):  
Excited State ◽  
Binding Energy ◽  
Electric Field ◽  
Excited States ◽  
Ground State ◽  
Heavy Hole ◽  
Single Particles ◽  
Lateral Electric Field ◽  
State Formula ◽  
Ground State Stability

The effect of the lateral electric field (LEF) on the excited and ground state stability of an exciton ([Formula: see text]) confined in a parabolic cylindrical quantum dot (QD) was estimated in this study. The calculation was performed in the framework of single-band effective mass theory using a variational approach. Our results revealed that the ground state binding energy of [Formula: see text] decreases with increasing the cylindrical QD radius until the exciton stability is lost at moderate LEF strength. By increasing the LEF strength, the excited heavy-hole ([Formula: see text]) can create an excited state [Formula: see text] or excited state [Formula: see text] of [Formula: see text], and the results indicate that the first state is more stable. In contrast, when an excited electron ([Formula: see text]) combines with an excited hole ([Formula: see text]) or unexcited hole ([Formula: see text]), it contains no split excited states for [Formula: see text] with less binding energy than the state [Formula: see text]. Comparing our previous results of donor impurity [Formula: see text] with [Formula: see text], we found that [Formula: see text] has a more stable ground state than [Formula: see text]. Moreover, the excited [Formula: see text] states are more stable than the excited states of [Formula: see text]. The quantum Stark shift (QSS) of the light- and heavy-hole exciton energy was explored, and a blue-shifted and quadratic QSS was observed. In contrast, for single particles (electron, heavy-hole and light hole), a red-shifted and linear QSS was observed.

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>

scholarly journals Photophysics of a copper phenanthroline elucidated by trajectory and wavepacket-based quantum dynamics: a synergetic approach

2017 ◽  
Vol 19 (30) ◽  
pp. 19590-19600 ◽  
Author(s):  
G. Capano ◽  
T. J. Penfold ◽  
M. Chergui ◽  
I. Tavernelli
Keyword(s):  
Molecular Dynamics ◽  
Excited State ◽  
Excited States ◽  
Ground State ◽  
Quantum Dynamics ◽  
Equilibrium Processes ◽  
Valuable Method ◽  
Non Equilibrium

On-the-fly excited state molecular dynamics is a valuable method for studying non-equilibrium processes in excited states and is beginning to emerge as a mature approach much like its ground state counterparts.

scholarly journals Measurements of n?g Coincidences in the Reaction 10B (d, n?)11C

1960 ◽  
Vol 13 (2) ◽  
pp. 99 ◽  
Author(s):  
JA McDonell ◽  
DG Sargood ◽  
JR Moroney ◽  
JR Prescott
Keyword(s):  
Excited State ◽  
Excited States ◽  
Ground State ◽  
State Transitions

The energies of some neutron groups leading to low excited states of "C in the reaction lOB(d,ny)"C have been measured. These lead to values of 4�3�0�3 MeV and 6�53 � O' 02 MeV for the energies of the second and fourth excited states respectively. y-Ray spectra have also been studied in coincidence with different neutron groups. Ground state transitions were observed from the second, third, and fourth excited states, together with cascade decays of the fourth excited state through each of the second and third. Deductions from these y-ray spectra considerably reduce the number of spin possibilities which have been found for these levels by other workers.

First-excited-state energy of hydrogenic impurity bound polaron in an anisotropic quantum dot in an electric field

2019 ◽  
Vol 33 (32) ◽  
pp. 1950386
Author(s):  
Shi-Hua Chen
Keyword(s):  
Excited State ◽  
Binding Energy ◽  
Quantum Dot ◽  
Electric Field ◽  
Binding Energies ◽  
Hydrogenic Impurity ◽  
Bound Polaron ◽  
First Excited State ◽  
Trial Wavefunction ◽  
Anisotropic Quantum Dot

The first-excited-state (ES) binding energy of hydrogenic impurity bound polaron in an anisotropic quantum dot (QD) is obtained by constructing a variational wavefunction under the action of a uniform external electric field. As for a comparison, the ground-state (GS) binding energy of the system is also included. We apply numerical calculations to KBr QD with stronger electron–phonon (E–P) interaction in which the new variational wavefunction is adopted. We analyzed specifically the effects of electric field and the effects of both the position of the impurity and confinement lengths in the xy-plane and the [Formula: see text] direction on the ground and the first-ES binding energies (BEs). The results show that the selected trial wavefunction in the ES is appropriate and effective for the current research system.

scholarly journals Study of Millimeter-Wave Rotational Spectra ofTrioxane in Ground, v(A), v1(E) = 1 and v2(E) = 1 States

2009 ◽  
Vol 6 (s1) ◽  
pp. S259-S279 ◽  
Author(s):  
Masoud Motamedi ◽  
Najmehalsadat Khademi
Keyword(s):  
Excited State ◽  
Excited States ◽  
Millimeter Wave ◽  
Ground State ◽  
Vibrational States ◽  
Rotational Spectra ◽  
First Time

The millimeter-wave rotational spectra of the ground and excited vibrational states v(A), v1(E) =1 and v2(E ) =1 of the oblate symmetric top molecule, (CH2O)3, have been analyzed again. The B0= 5273.25747MHz, DJ= 1.334547 kHz, DJk= -2.0206 kHz, HJ(-1.01 mHz), HJK(-3.80 mHz), and HKJ(4.1 mHz) have been determined for ground state. For non degenerate excited state, vA(1), the B = 5260.227723 MHz and DJand DJKwere determined 1.27171 kHz and -1.8789 kHz respectively. The 1=±1 series have been assigned in two different excited states v1(E) =1 and v2(E) =1.Most of the parameters were determined with higher accuracy compare with before. For the v2(E) =1 state the Cζ=-1940.54(11) MHz and qJ= 0.0753 (97) kHz were determined for the first time.

BOUND POLARON IN A POLAR SEMICONDUCTOR HETEROJUNCTION IN STATIC ELECTRIC FIELD

2006 ◽  
Vol 20 (17) ◽  
pp. 2359-2368 ◽  
Author(s):  
JIA LIU ◽  
JING-LIN XIAO
Keyword(s):  
Binding Energy ◽  
Electric Field ◽  
Ground State ◽  
Longitudinal Optical ◽  
Static Electric Field ◽  
Phonon Modes ◽  
Potential Approximation ◽  
Intermediate Coupling ◽  
Area Density ◽  
Bound Polaron

The binding energy of the ground state of a bound polaron near the interface of a polar-polar semiconductor heterojunction is investigated by using the Lee–Low–Pines intermediate coupling method. The influence of a triangular potential approximation of the interface, the electron-phonon and impurity-phonon interactions as well as the half-space bulk longitudinal and interface-optical phonon modes are all taken into account. We have performed numerical calculations on the GaAs / Al x Ga 1-x As (0.2 ≤ x ≤ 0.4) heterojunction system and studied the relations between the ground state binding energy of the polaron and the impurity position, electric field strength and electron area density, respectively. It is found that with the increase in the distance between the impurity and the interface, the binding energy and the contribution of phonons reach the maximum. It is also found that the binding energy of the bound polaron increases slowly with the increase in an electric field while the total polaronic correction decreases the binding energy. When the electron area density is increased, the contribution of the interface-optical (IO) modes is greater than that of the bulk longitudinal optical (LO) mode.

Determination of Ionization Efficiencies of Excited Atoms in a Flame by Laser-Enhanced Ionization Spectrometry

1989 ◽  
Vol 43 (6) ◽  
pp. 940-952 ◽  
Author(s):  
O. Axner ◽  
T. Berglind
Keyword(s):  
Excited State ◽  
Excited States ◽  
Ground State ◽  
Energy Difference ◽  
Ionization Efficiency ◽  
Striking Feature ◽  
Boltzmann Factor ◽  
Excited Atoms ◽  
Ionization Limit

State-specific ionization efficiencies for excited Li and Na atoms in acetylene/air flames have been determined. The ionization efficiencies, i.e., the probability that the excited atoms ionize instead of returning to the ground state, are determined by relating collision-assisted Laser-Enhanced Ionization (LEI) signals from various excited states with laser-induced photoionization signals. The ionization efficiencies are found to decrease (from being one at the ionization limit) almost monotonically as the lower atoms are excited. The most striking feature, however, is that the decrease of the ionization efficiency values is generally found to be less than the decrease of the Boltzmann factor, exp(- δE/kT), when the energy difference, δE, between the excited state and the ionization limit is increased. The ionization efficiencies are found to be close to unity for states with δE < kT and approximately 50% for states with δE ≈ 2.5 kT ( np ≈ 6 p). For the lower states, the ionization efficiencies are found to be approximately five times larger than the Boltzmann factor.

Theoretical Study of Density Function Theory on Excited States of Methyl Methacrylate

2011 ◽  
Vol 233-235 ◽  
pp. 2871-2874
Author(s):  
Zhi Xong Huang ◽  
Gang Qin ◽  
Ming Zhang ◽  
Yan Qin ◽  
Lian Meng Zhang
Keyword(s):  
Excited State ◽  
Methyl Methacrylate ◽  
Excitation Energy ◽  
Excited States ◽  
Ground State ◽  
Theoretical Study ◽  
Function Theory ◽  
Density Function Theory ◽  
Molecular Structures ◽  
Homo And Lumo

The excited states of methyl methacrylate(MMA) were calculated by CIS method, MMA molecules on the ground and excited states of molecular structures were optimized. The HOMO and LUMO molecular orbitals of MMA molecule are given in the ground state and excited state . The results show that: MMA is excited, the molecular orbital from 27 → 28, the excitation energy is 1.4310eV, Carbon-carbon（C=C）double bonds break.

Excited State Polarizability of Some Polycyclic Polyenes

2017 ◽  
Vol 68 (2) ◽  
pp. 307-310 ◽  
Author(s):  
Ana Maria Ciubara ◽  
Andreea Celia Benchea ◽  
Carmen Beatrice Zelinschi ◽  
Dana Ortansa Dorohoi
Keyword(s):  
Excited State ◽  
Absorption Spectra ◽  
Excited States ◽  
Electronic Absorption ◽  
Ground State ◽  
Electronic Absorption Spectra ◽  
Photon Absorption ◽  
Absorption Process ◽  
Polar Solvents ◽  
Molecular Parameters

The electronic absorption spectra of five polycyclic polyenes were recorded in non-polar solvents in order to determine their polarizability in excited states from the strength of the dispersive interactions in their diluted solutions. The bathochromic shifts of p-p* vibronic bands prove the increase of the molecular polarizabilty in the photon absorption process. Some molecular parameters of the analyzed polyenes in their ground state were computed by using the programs from Spartan�14.

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