scholarly journals Transient Absorption of DNA bases in the gas phase and in chloroform solution: a comparative quantum mechanical study

2021 ◽  
Author(s):  
Daniil A. Fedotov ◽  
Alexander C. Paul ◽  
Henrik Koch ◽  
Fabrizio Santoro ◽  
Sonia Coriani ◽  
...  
Keyword(s):  
Gas Phase ◽  
Density Functional ◽  
Transient Absorption ◽  
Chloroform Solution ◽  
Excited State Absorption ◽  
Polarizable Continuum Model ◽  
Photon Absorption ◽  
Dna Bases ◽  
Quantum Mechanical ◽  
Mechanical Methods

We study the excited state absorption (ESA) properties of the four DNA bases (thymine, cytosine, adenine, and guanine) by different single reference quantum mechanical methods, i.e. equation of motion coupled cluster singles and doubles (EOM-CCSD), singles, doubles and perturbative triples (EOM-CC3), and time-dependent density functional theory (TD-DFT), with the long-range corrected CAM-B3LYP functional. Preliminary results at the Tamm-Dancoff (TDA) CAM-B3LYP level using the maximum overlap method (MOM) are reported for Thymine. In the gas phase, the three methods predict similar One Photon Absorption (OPA) spectra, which are also consistent with the experimental results and with the most accurate computational studies available in the literature. The ESA spectra are then computed for the pp  states (one for pyrimidine, two for purines) associated with the lowest energy absorption band, and for the close-lying np  state. The EOM-CC3, EOM-CCSD and CAM-B3LYP methods provide similar ESA spectral patterns, which are also in qualitative agreement with literature RASPT2 results. Once validated in the gas phase, TD-CAM-B3LYP has been used to compute the ESA in chloroform, including solvent effect by the polarizable continuum model (PCM). The predicted OPA and ESA spectra in chloroform are very similar to those in the gas phase, most of the bands shifting by less than 0.1 eV, with a small increase of the intensities and a moderate destabilization of the np  state. Finally, ESA spectra have been computed from the minima of the lowest energy pp  state, and are consistent with the available experimental transient absorption spectra of the nucleosides in solution, providing a final validation of our computational approach.

scholarly journals Tuning of Hyperpolarizability, One- and Two-Photon Absorption of D-A and D-A-A Type Intramolecular Charge Transfer Based Sensors

2019 ◽  
Author(s):  
Pralok K. Samanta ◽  
Md Mehboob Alam ◽  
Ramprasad Misra ◽  
Swapan K. Pati
Keyword(s):  
Charge Transfer ◽  
Gas Phase ◽  
Density Functional ◽  
Intramolecular Charge Transfer ◽  
Photon Absorption ◽  
First Hyperpolarizability ◽  
Two Photon Absorption ◽  
Two Photon ◽  
Nlo Response ◽  
Donor Acceptor

Solvents play an important role in shaping the intramolecular charge transfer (ICT) properties of π-conjugated molecules, which in turn can affect their one-photon absorption (OPA) and two-photon absorption (TPA) as well as the static (hyper)polarizabilities. Here, we study the effect of solvent and donor-acceptor arrangement on linear and nonlinear optical (NLO) response properties of two novel ICT-based fluorescent sensors, one consisting of hemicyanine and dimethylaniline as electron withdrawing and donating groups (molecule 1), respectively and its boron-dipyrromethene (BODIPY, molecule 2)-fused counterpart (molecule 3). Density functional theoretical (DFT) calculations using long-range corrected CAM-B3LYP and M06-2X functionals, suitable for studying properties of ICT molecules, are employed to calculate the desired properties. The dipole moment (µ) as well as the total first hyperpolarizability (β<sub>total</sub>) of the studied molecules in the gas phase is dominantly dictated by the component in the direction of charge transfer. The ratios of vector component of first hyperpolarizability (β<sub>vec</sub>) to β<sub>total</sub> also reveal unidirectional charge transfer process. The properties of the medium significantly affect the OPA, hyperpolarizability and TPA properties of the studied molecules. Time dependent DFT (TDDFT) calculations suggest interchanging between two lowest excited states of molecule 3 from the gas phase to salvation. The direction of charge polarization and dominant transitions among molecular orbitals involved in the OPA and TPA processes are studied. The results presented are expected to be useful in tuning the NLO response of many ICT-based chromophores, especially those with BODIPY acceptors.<br>

Workshop on „the Applications of Quantum Mechanical Methods in Gas Phase Ion Chemistry“

1999 ◽  
pp. 431-444
Author(s):  
J. HruŠák ◽  
J. F. Liebman ◽  
P. P. Gaspar ◽  
D. J. Berger ◽  
E. Leere Oiestad ◽  
...  
Keyword(s):  
Gas Phase ◽  
Quantum Mechanical ◽  
Ion Chemistry ◽  
Gas Phase Ion Chemistry ◽  
Mechanical Methods ◽  
Gas Phase Ion

scholarly journals Excited State Absorption of Uracil in the Gas Phase: Mapping the Main Decay Paths by Different Electronic Structure Methods

2020 ◽  
Author(s):  
Daniil Fedotov ◽  
Alexander C. Paul ◽  
Paolo Posocco ◽  
Fabrizio Santoro ◽  
Marco Garavelli ◽  
...  
Keyword(s):  
Electronic Structure ◽  
Excited State ◽  
Gas Phase ◽  
Absorption Spectra ◽  
Potential Energy Surfaces ◽  
Transient Absorption ◽  
Computational Study ◽  
Excited State Absorption ◽  
High Energy ◽  
Electronic Structure Methods

We present a computational study of the one-photon and excited-state absorption from the two lowest-energy excited states of uracil in the gas phase: an n?pi* dark state<br>(1n) and the lowest-energy bright ??? pi-pi* state (1?pi). The predictions of six di?fferent linear response electronic structure methods, namely TD-CAM-B3LYP, EOM-CCSD,<br>EOM-CC3, ADC(2), ADC(2)-x and ADC(3) are critically compared. In general, the spectral shapes predicted by TD-CAM-B3LYP, EOM-CCSD, EOM-CC3 and ADC(3) are fairly similar, though the quality of TD-CAM-B3LYP slightly deteriorates in the high energy region. Computing the spectra at some key structures on the di?fferent potential energy surfaces (PES), i.e. the Franck-Condon point, the 1n minimum,<br>and structures representative of di?fferent regions of the 1? PES, we obtain important insights into the shift of the excited-state absorption spectra, following the motion of the<br>wavepacket on the excited state PES. Though 1pi ? has larger excited-state absorption than 1n, some spectral regions are dominated by these latter signals. Aside from its<br>methodological interest, we thus obtain interesting indications to interpret transient absorption spectra to disentangle the photoactivated dynamics of nucleobases.

scholarly journals Excited State Absorption of Uracil in the Gas Phase: Mapping the Main Decay Paths by Different Electronic Structure Methods

2020 ◽  
Author(s):  
Daniil Fedotov ◽  
Alexander C. Paul ◽  
Paolo Posocco ◽  
Fabrizio Santoro ◽  
Marco Garavelli ◽  
...  
Keyword(s):  
Electronic Structure ◽  
Excited State ◽  
Gas Phase ◽  
Absorption Spectra ◽  
Potential Energy Surfaces ◽  
Transient Absorption ◽  
Computational Study ◽  
Excited State Absorption ◽  
High Energy ◽  
Electronic Structure Methods

We present a computational study of the one-photon and excited-state absorption from the two lowest-energy excited states of uracil in the gas phase: an n?pi* dark state<br>(1n) and the lowest-energy bright ??? pi-pi* state (1?pi). The predictions of six di?fferent linear response electronic structure methods, namely TD-CAM-B3LYP, EOM-CCSD,<br>EOM-CC3, ADC(2), ADC(2)-x and ADC(3) are critically compared. In general, the spectral shapes predicted by TD-CAM-B3LYP, EOM-CCSD, EOM-CC3 and ADC(3) are fairly similar, though the quality of TD-CAM-B3LYP slightly deteriorates in the high energy region. Computing the spectra at some key structures on the di?fferent potential energy surfaces (PES), i.e. the Franck-Condon point, the 1n minimum,<br>and structures representative of di?fferent regions of the 1? PES, we obtain important insights into the shift of the excited-state absorption spectra, following the motion of the<br>wavepacket on the excited state PES. Though 1pi ? has larger excited-state absorption than 1n, some spectral regions are dominated by these latter signals. Aside from its<br>methodological interest, we thus obtain interesting indications to interpret transient absorption spectra to disentangle the photoactivated dynamics of nucleobases.

Single State Absorption Spectra of Novel Nonlinear Optical Materials

1999 ◽  
Vol 597 ◽  
Author(s):  
Sean M. Kirkpatrick ◽  
Casey Clark ◽  
Richard L. Sutherland
Keyword(s):  
Excited State ◽  
Cross Section ◽  
Transient Absorption ◽  
Short Pulse ◽  
Measurement Techniques ◽  
Excited State Absorption ◽  
Leading Edge ◽  
Photon Absorption ◽  
Two Photon ◽  
Pulse Pump

AbstractDuring the absorption of a laser pulse of moderate length, the leading edge can experience excited state absorption out of the first singlet state. The measurement of this excited state absorption spectrum can only be accurately probed using short pulse pump-probe techniques. Specifically, we examine the excited state absorption of AF-380 in THF using ultrafast transient white light absorption spectroscopy (TWLA). This material has been the focus of several investigations due to it's purported large two-photon absorption cross-section, the discrepancies between long and short pulse measurements, and it's use in holographic twophoton induced photopolymerization. It is believed that a substantial excited state absorbance can account for the difference in two-photon cross section measurements. It is also possible that this excited state exhibits coherence for time scales that can affect further absorption of longer pump pulses. We examine the transient absorption of this species, as well as polarization and free carrier effects and discuss the possible implications with regards to measurement techniques.

STUDY OF THE S1 AND S2 EXCITED STATES OF GAS-PHASE PROTONATED SCHIFF BASE RETINAL CHROMOPHORES IN ONE AND TWO PHOTON ABSORPTION

2011 ◽  
Vol 10 (02) ◽  
pp. 121-132 ◽  
Author(s):  
YUANZUO LI ◽  
PENG SONG ◽  
YING SHI ◽  
YONG DING ◽  
FENGJIE ZHOU ◽  
...  
Keyword(s):  
Schiff Base ◽  
Excited State ◽  
Charge Transfer ◽  
Gas Phase ◽  
Excited States ◽  
Density Functional ◽  
Three Dimensional ◽  
Photon Absorption ◽  
Two Photon ◽  
The One

The S1 and S2 excited states of gas-phase protonated Schiff base retinal chromophores in the one- and two-photon absorptions (TPAs) are investigated with time-dependent density functional theory. In one-photon absorption, the two-dimensional (2D) site and three-dimensional (3D) cube representations reveal that S1 and S2 excited states of gas-phase protonated Schiff base retinal chromophores are all charge transfer excited states. To better study the weak S2 excited states of gas-phase protonated Schiff base retinal chromophores, we investigated theoretically excited state properties of them in TPA. For 11-cis dimethyl retinal, it is found that the cross section of S2 excited state is 51.04 GM in PTA, which is only slightly smaller than that of S1 (77.04 GM) in TPA. Therefore, the S2 excited state of 11-cis dimethyl retinal can be clearly observed in TPA experiment. The 2D site and 3D cube representations reveal that electronic transition from S1 to S2 excited state of gas-phase protonated Schiff base retinal chromophores in TPA are also of charge transfer character.

DFT calculation of crystallographic properties of dioctahedral 2:1 phyllosilicates

Clay Minerals ◽  
2008 ◽  
Vol 43 (3) ◽  
pp. 351-361 ◽  
Author(s):  
J. Ortega-Castro ◽  
N. Hernández-Haro ◽  
A. Hernández-Laguna ◽  
C. I. Sainz-Díaz
Keyword(s):  
Density Functional ◽  
Basis Sets ◽  
Quantum Mechanical ◽  
Functional Theory ◽  
Oh Groups ◽  
Low Degree ◽  
Mechanical Methods ◽  
Weak Interlayer ◽  
Low Charge ◽  
Cation Substitutions

AbstractThe low-charge dioctahedral 2:1 phyllosilicates are an important group of clay minerals that have a low degree of cation substitution and very weak interlayer interatomic interactions which are difficult to reproduce with quantum mechanical calculations. In order to study the crystallographic properties of these compounds with density functional theory (DFT) quantum-mechanical methods, an optimization of norm-conserving pseudopotentials of Al, Si, O, H and Na atoms has been carried out, and an optimization of the cutoff radii of the basis sets has been accomplished. Crystallographic properties and vibrational stretching frequencies of the OH groups, ν(OH), have been calculated, being consistent with previous computational and experimental results. All frequencies can be related to the different molecular environment of the OH groups. The effect of octahedral Fe3+ substitution on the ν(OH) frequency is reproduced. Several configurations of cation substitutions and interlayer cation (IC) positions are studied in low-charge dioctahedral 2:1 phyllosilicates, such as Al4(Si7–xAlx)O20(OH)4Nax, with x = 0.25, 0.50 and 0.75, indicating that the IVAl3+ is highly dispersed and the IC tends to be in the substituted ditrigonal hole. For the Al4(Si7Al)O20(OH)4Na composition, the trans-vacant form is more stable than the cis-vacant one.

scholarly journals Tuning of Hyperpolarizability, One- and Two-Photon Absorption of D-A and D-A-A Type Intramolecular Charge Transfer Based Sensors

2019 ◽  
Author(s):  
Pralok K. Samanta ◽  
Md Mehboob Alam ◽  
Ramprasad Misra ◽  
Swapan K. Pati
Keyword(s):  
Charge Transfer ◽  
Gas Phase ◽  
Density Functional ◽  
Intramolecular Charge Transfer ◽  
Photon Absorption ◽  
First Hyperpolarizability ◽  
Two Photon Absorption ◽  
Two Photon ◽  
Nlo Response ◽  
Donor Acceptor

Solvents play an important role in shaping the intramolecular charge transfer (ICT) properties of π-conjugated molecules, which in turn can affect their one-photon absorption (OPA) and two-photon absorption (TPA) as well as the static (hyper)polarizabilities. Here, we study the effect of solvent and donor-acceptor arrangement on linear and nonlinear optical (NLO) response properties of two novel ICT-based fluorescent sensors, one consisting of hemicyanine and dimethylaniline as electron withdrawing and donating groups (molecule 1), respectively and its boron-dipyrromethene (BODIPY, molecule 2)-fused counterpart (molecule 3). Density functional theoretical (DFT) calculations using long-range corrected CAM-B3LYP and M06-2X functionals, suitable for studying properties of ICT molecules, are employed to calculate the desired properties. The dipole moment (µ) as well as the total first hyperpolarizability (β<sub>total</sub>) of the studied molecules in the gas phase is dominantly dictated by the component in the direction of charge transfer. The ratios of vector component of first hyperpolarizability (β<sub>vec</sub>) to β<sub>total</sub> also reveal unidirectional charge transfer process. The properties of the medium significantly affect the OPA, hyperpolarizability and TPA properties of the studied molecules. Time dependent DFT (TDDFT) calculations suggest interchanging between two lowest excited states of molecule 3 from the gas phase to salvation. The direction of charge polarization and dominant transitions among molecular orbitals involved in the OPA and TPA processes are studied. The results presented are expected to be useful in tuning the NLO response of many ICT-based chromophores, especially those with BODIPY acceptors.<br>

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