Search results for "Excitation"
showing 10 items of 1290 documents
Vertical spectrum of ethene: uncontracted versus contracted correlation methods and the role of the adapted molecular orbitals
1998
Abstract Ethylene vertical excitation energies (VEE) below 9.5 eV have been calculated with the complete active-space singles and doubles configuration interaction self-consistent size-consistent dressing (SC) 2 CAS–SDCI. The mean of the absolute deviation from experiment for the calculated VEE are 0.14, 0.05 and 0.03 eV for three different molecular orbital (MO) sets tried. The results show that an uncontracted method and a realistic MO set avoid the difficulties present in the calculation of the strongly mixed Rydberg-valence 1B 1u states.
Dynamics behind the long-lived coherences of I2 in solid Xe.
2013
The absorption spectrum of I2 in solid Xe shows resolved zero-phonon lines and phonon side bands near the origin of the B←X transition (550-625 nm). The long-lived |B⟩⟨X| coherence in this energy range (T2 = 600 fs on average) emerges as vibrationally unrelaxed fluorescence in resonance Raman (RR) spectra. Upon excitation in the structureless continuum at 532 nm, the oscillatory RR progression exhibits electronic dephasing time of T2 = 150 fs. Two RR progressions with markedly different vibrational coherence on the X-state are observed. The main progression of sharp overtones (T221 ps) is assigned to molecules trapped in double-substitution sites. The minor progression, which shows dephasin…
Long-Lived Electronic Coherence of Iodine in the Condensed Phase: Sharp Zero-Phonon Lines in the B↔X Absorption and Emission of I2 in Solid Xe
2015
Our study of B←X absorption of molecular iodine (I2) isolated in a low-temperature crystalline xenon has revealed an exceptionally long-lived electronic coherence in condensed phase conditions. The visible absorption spectrum shows prominent vibronic structure in the form of zero-phonon lines (ZPLs) and phonon side bands (PSBs). The resolved spectrum implies weak interaction of the chromophore to the lattice degrees of freedom. The coherence extends past the vibrational period of the excited state molecule, unlike that observed in any condensed phase environment for I2 so far. The ZP transitions from the relaxing B-state populations were resolved in the hot luminescence when the 532 nm lase…
Femtosecond up-conversion technique for probing the charge transfer in a P3HT : PCBM blend via photoluminescence quenching
2009
We report on an experimental study of the charge transfer dynamics in a P3HT : PCBM blend by means of a femtosecond fluorescence up-conversion technique. Using two-photon excitation we probe the exciton dynamics in P3HT and a P3HT : PCBM blend with a weight ratio of 1 : 1 at excitation densities of up to 6 × 1018 cm−3. In both samples we find strongly nonexponential decay traces compatible with (i) diffusion-limited exciton–exciton annihilation and (ii) diffusion-limited donor–acceptor charge transfer in the polymer blend. Additionally, our results indicate that in the P3HT : PCBM blend about 50% of the photogenerated excitons undergo a prompt charge transfer process on a time scale of abou…
Does the Recruitment of Excitation and Inhibition in the Motor Cortex Differ?
2007
The level of excitability within the motor cortex can be described as a balance between excitation and inhibition, but it is unknown how well both processes correlate. To address this question, the authors measured motor cortical excitability and inhibition in healthy human subjects, comparing the recruitment of motor evoked potentials (MEPs) and the duration of the cortical silent period (CSP) after transcranial magnetic stimulation (TMS). Single-pulse "focal" TMS was applied at intensities varying between 90% and 200% of motor thresholds to the right motor cortex of 15 healthy volunteers. The peak-to peak size of MEP responses and the duration of the CSP were measured in small hand muscle…
Sexual Inhibition and Sexual Excitation Scales in Men: Psychometric Properties of a Polish Adaptation.
2020
AbstractThe present study aimed to develop a Polish version of the Sexual Inhibition/Sexual Excitation Scale (SIS/SES-PL) and explore its psychometric validity in a sample of 498 men aged between 18 and 55 years. We used exploratory and confirmatory factor analyses to obtain the best model fit. Out of the 45 items in the original scale, 32 items with eight subscales and three higher-order factors: (sexual excitation [SES], sexual inhibition due to performance failure [SIS1], and sexual inhibition due to performance consequences [SIS2]) were included in the SIS/SES-PL. The SIS/SES-PL was found to have a good and satisfactory fit (comparative fit index = .87; Tucker–Lewis Index = .85; root me…
Electronic excitations of 1,4-disilyl-substituted 1,4-disilabicycloalkanes: a MS-CASPT2 study of the influence of cage size.
2007
We present a multistate complete active space second-order perturbation theory computational study aimed to predict the low-lying electronic excitations of four compounds that can be viewed as two disilane units connected through alkane bridges in a bicyclic cage. The analysis has focused on 1,4-disilyl-1,4-disilabicyclo[2.2.1]heptane (1a), 1,4-bis(trimethylsilyl)-1,4-disilabicyclo[2.2.1]heptane (1b), 1,4-disilyl-1,4-disilabicyclo[2.1.1]hexane (2a), and 1,4-bis(trimethylsilyl)-1,4-disilabicyclo[2.1.1]hexane (2b). The aim has been to find out the nature of the lowest excitations with significant oscillator strengths and to investigate how the cage size affects the excitation energies and the…
Gain lifetime measurement of a Ni-like Ag soft X-ray laser
2012
International audience; Experimental results of a two-stage Ni-like Ag soft X-ray laser operated in a seed-amplifier configuration are presented. Both targets were pumped applying the double-pulse grazing incidence technique with intrinsic travelling wave excitation. The injection of the seed X-ray laser into the amplifier target was realized by a spherical mirror. The results show amplification of the seed X-ray laser and allow for a direct measurement of the gain lifetime. The experimental configuration is suitable for providing valuable input for computational simulations. (C) 2012 Optical Society of America
Amplified spontaneous emission in thin films of quasi-2D BA3MA3Pb5Br16 lead halide perovskites
2021
Quasi-2D (two-dimensional) hybrid perovskites are emerging as a new class of materials with high photoluminescence yield and improved stability compared to their three-dimensional (3D) counterparts. Nevertheless, despite their outstanding emission properties, few studies have been reported on amplified spontaneous emission (ASE) and a thorough understanding of the photophysics of these layered materials is still lacking. In this work, we investigate the ASE properties of multilayered quasi-2D BA3MA3Pb5Br16 films through the dependence of the photoluminescence on temperature and provide a novel insight into the emission processes of quasi-2D lead bromide perovskites. We demonstrate that the …
A modified ansatz for explicitly correlated coupled-cluster wave functions that is suitable for response theory
2009
A modified ansatz for explicitly correlated coupled-cluster wave functions with a single correlation factor is set forward. It is based on the fixed amplitude ansatz of Ten-no [Chem. Phys. Lett. 398, 56 (2004)] to which an extra term is added that allows for the explicitly correlated description of singly excited configurations. The new approach has been implemented for coupled-cluster singles and doubles with the aid of automated techniques. Numerical results are presented for vertical excitation energies, and ground and excited state equilibrium distances and harmonic frequencies of diatomics. The new approach is shown to provide a nearly unbiased description of ground and predominantly s…