scholarly journals Control of the atom (nucleus) lifetime in the excited state by means of a low-frequency external field

2002 ◽  
Vol 35 (19) ◽  
pp. 3957-3965 ◽  
Author(s):  
I D Feranchuk ◽  
L I Komarov ◽  
A Ulyanenkov
Keyword(s):  
Excited State ◽  
External Field ◽  
Low Frequency ◽  
Atom Nucleus

scholarly journals Vibronic coherence evolution in multidimensional ultrafast photochemical processes

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
James D. Gaynor ◽  
Jason Sandwisch ◽  
Munira Khalil
Keyword(s):  
Excited State ◽  
Charge Transfer ◽  
Vibrational Spectroscopy ◽  
Low Frequency ◽  
Coherence Transfer ◽  
Transfer Energy ◽  
Electronic Delocalization ◽  
Vibronic States ◽  
High Frequency Vibrations ◽  
Vibronic Couplings

AbstractThe complex choreography of electronic, vibrational, and vibronic couplings used by photoexcited molecules to transfer energy efficiently is remarkable, but an unambiguous description of the temporally evolving vibronic states governing these processes has proven experimentally elusive. We use multidimensional electronic-vibrational spectroscopy to identify specific time-dependent excited state vibronic couplings involving multiple electronic states, high-frequency vibrations, and low-frequency vibrations which participate in ultrafast intersystem crossing and subsequent relaxation of a photoexcited transition metal complex. We discover an excited state vibronic mechanism driving long-lived charge separation consisting of an initial electronically-localized vibrational wavepacket which triggers delocalization onto two charge transfer states after propagating for ~600 femtoseconds. Electronic delocalization consequently occurs through nonadiabatic internal conversion driven by a 50 cm−1 coupling resulting in vibronic coherence transfer lasting for ~1 picosecond. This study showcases the power of multidimensional electronic-vibrational spectroscopy to elucidate complex, non-equilibrium energy and charge transfer mechanisms involving multiple molecular coordinates.

scholarly journals Excited State Frequencies of Chlorophyll f and Chlorophyll a and Evaluation of Displacement through Franck-Condon Progression Calculations

Molecules ◽  
2019 ◽  
Vol 24 (7) ◽  
pp. 1326 ◽  
Author(s):  
Noura Zamzam ◽  
Jasper van Thor
Keyword(s):  
Excited State ◽  
Chlorophyll A ◽  
High Frequency ◽  
Vibrational Mode ◽  
Low Frequency ◽  
State Frequency ◽  
B3lyp Calculations ◽  
Resonant Raman ◽  
Franck Condon ◽  
Chlorophyll F

We present ground and excited state frequency calculations of the recently discovered extremely red-shifted chlorophyll f. We discuss the experimentally available vibrational mode assignments of chlorophyll f and chlorophyll a which are characterised by particularly large downshifts of 131-keto mode in the excited state. The accuracy of excited state frequencies and their displacements are evaluated by the construction of Franck–Condon (FC) and Herzberg–Teller (HT) progressions at the CAM-B3LYP/6-31G(d) level. Results show that while CAM-B3LYP results are improved relative to B3LYP calculations, the displacements and downshifts of high-frequency modes are underestimated still, and that the progressions calculated for low temperature are dominated by low-frequency modes rather than fingerprint modes that are Resonant Raman active.

Slow magnetic relaxation in a μ1,1′-azido cobalt(ii) methylquinoline chain complex

2018 ◽  
Vol 47 (44) ◽  
pp. 15745-15750 ◽  
Author(s):  
Cyril Rajnák ◽  
Ľubor Dlháň ◽  
Ján Moncol ◽  
Ján Titiš ◽  
Roman Boča
Keyword(s):  
Relaxation Time ◽  
External Field ◽  
Magnetic Relaxation ◽  
Low Frequency ◽  
Chain Complex ◽  
Frequency Mode ◽  
Chain Architecture ◽  
1D Chain ◽  
Slow Magnetic Relaxation ◽  
Low Frequency Mode

A [Co(N3)2(mqu)] complex with a 1D chain architecture (mqu – 4-methylquinoline) shows slow magnetic relaxation with three distinct modes. The relaxation time strongly depends upon the applied external field. The low-frequency mode exhibits a relaxation time longer than one second: τLF = 1.6(2) s at BDC = 0.8 T and T = 1.9 K.

Induced absorption and stimulated emission in a driven two-level atom

1992 ◽  
Vol 70 (6) ◽  
pp. 427-431 ◽  
Author(s):  
Constantine Mavroyannis
Keyword(s):  
Excited State ◽  
Ground State ◽  
Laser Field ◽  
Low Frequency ◽  
Ultrashort Pulses ◽  
Stimulated Emission ◽  
Spectral Lines ◽  
Laser Photon ◽  
Induced Absorption ◽  
Level Atom

We have considered the induced processes that occur in a driven two-level atom, where a laser photon is absorbed and emitted by the ground and by the excited states of the atom, respectively. In the low-intensity limit of the laser field, the induced spectra arising when a laser photon is absorbed by the ground state of the atom consist of two peaks describing induced-absorption and stimulated-emission processes, respectively, where the former prevails over the latter. Asymmetry of the spectral lines occurs at off-resonance and its extent depends on the detuning of the laser field. The physical, process where a laser photon is emitted by the excited state is the reverse of that arising from the absorption of a laser photon by the ground state of the atom. The former differs from the latter in that the emission of a laser photon by the excited state occurs in the low-frequency regime and that the stimulated-emission process prevails over that of the induced absorption. In this case, amplification of ultrashort pulses is likely to occur without the need of population inversion between the optical transitions. The computed spectra are graphically presented and discussed.

Phase Interference in the Two-Photon Excitation of Phenanthrene

1986 ◽  
Vol 40 (4) ◽  
pp. 486-489
Author(s):  
A. C. Koskelo ◽  
D. L. Curtin ◽  
M. J. Wirth
Keyword(s):  
Excited State ◽  
Vapor Phase ◽  
Low Frequency ◽  
Photon Polarization ◽  
Symmetric State ◽  
Two Photon ◽  
Photon Excitation ◽  
Antisymmetric State ◽  
First Excited State ◽  
Phase Interference

Two-photon polarization measurements are shown to provide an incorrect symmetry assignment for the first excited state of phenanthrene, both in solution and in the vapor phase. Published assignments from one-photon, single-crystal measurements indicate a totally symmetric state, while the assignment from two-photon measurements indicates an antisymmetric state. Possible reasons for the failure of the two-photon symmetry assignment are low-frequency vibronic overlap, and interference among the diagonal tensor elements. Experimental evidence points to interference as the origin of the discrepancy.

Spectrum of azulene. VI. Centrifugal distortion and the inertial defect

1969 ◽  
Vol 22 (1) ◽  
pp. 1 ◽  
Author(s):  
AJ McHugh ◽  
IG Ross
Keyword(s):  
Excited State ◽  
Low Frequency ◽  
Coupling Constants ◽  
Centrifugal Distortion ◽  
Vibrationally Excited ◽  
Normal Vibrations ◽  
Out Of Plane ◽  
Electronically Excited ◽  
Planar Molecules ◽  
Centrifugal Distortion Constants

The published microwave spectrum of azulene is re-analysed to yield the following values of the centrifugal distortion constants (units of kHz): Taaaa -1.45�0.76; Tbbbb -0.05�0.07; Taabb +0.70�0.42; Tabab -0.47�0.17. ��� The inertial defect Δ = Ic-Ia-Ib, typically positive in monocyclic compounds, is negative in azulene. According to the theory of Oka and Morino, the largest contribution to Δ is the vibrational part, which depends on the frequencies of the normal vibrations and on the Coriolis coupling constants. For the latter, a modified ?uniform coupling? approximation is proposed, based on sum rules applicable to planar molecules. Calculations are then carried out on pyridine, naphthalene, and azulene in which the change of sign of Δ, in two-ring, and presumably larger, aromatics is traced to the influence of low- frequency out-of-plane vibrations. For azulene, the values of Δ in a vibrationally excited state and an electronically excited state are also considered.

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