scholarly journals Interstellar nitrile anions: Detection of C3N− and C5N− in TMC-1

2020 ◽  
Vol 641 ◽  
pp. L9 ◽  
Author(s):  
J. Cernicharo ◽  
N. Marcelino ◽  
J. R. Pardo ◽  
M. Agúndez ◽  
B. Tercero ◽  
...  
Keyword(s):  
Excited State ◽  
Strong Support ◽  
Carbon Chain ◽  
Formation Mechanisms ◽  
Circumstellar Envelope ◽  
Vibrationally Excited ◽  
Neutral Radical ◽  
Taurus Region ◽  
Dark Core

We report on the first detection of C3N− and C5N− towards the cold dark core TMC-1 in the Taurus region, using the Yebes 40 m telescope. The observed C3N/C3N− and C5N/C5N− abundance ratios are ∼140 and ∼2, respectively; that is similar to those found in the circumstellar envelope of the carbon-rich star IRC +10216. Although the formation mechanisms for the neutrals are different in interstellar (ion-neutral reactions) and circumstellar clouds (photodissociation and radical-neutral reactions), the similarity of the C3N/C3N− and C5N/C5N− abundance ratios strongly suggests a common chemical path for the formation of these anions in interstellar and circumstellar clouds. We discuss the role of radiative electronic attachment, reactions between N atoms and carbon chain anions Cn−, and that of H− reactions with HC3N and HC5N as possible routes to form CnN−. The detection of C5N− in TMC-1 gives strong support for assigning to this anion the lines found in IRC +10216, as it excludes the possibility of a metal-bearing species, or a vibrationally excited state. New sets of rotational parameters have been derived from the observed frequencies in TMC-1 and IRC +10216 for C5N− and the neutral radical C5N.

scholarly journals Role of Electronic Excited State in Kinetics of the CH2OO + SO2 ! HCHO + SO3 Reaction

2021 ◽  
Author(s):  
Qingfei Song ◽  
Qiuyu Zhang ◽  
Qingyong Meng
Keyword(s):  
Excited State ◽  
Room Temperature ◽  
Energy Surface ◽  
Regression Method ◽  
Vibrationally Excited ◽  
Compute Data ◽  
Ring Polymer ◽  
Experimental Values ◽  
Kinetics Of

In this work, kinetics of the CH2OO + SO2 ! HCHO + SO3 reaction was studied by ring-polymer molecular dynamics (RPMD). To perform RPMD calculations, multi-reference configuration interaction (MRCI) was first carried out to compute data for constructing potential energy surface (PES) through a kernel regression method. On the basis of the present MRCI calculations, the statics multi-state mechanism involving the lowest-lying singlet excited state (denoted by S 1) was proposed, which is di?erent from the previously proposed mechanism with the lowest-lying triplet state (denoted by T1). Moreover, the present RPMD calculations predicted the rate coe?cient of 3:95?10􀀀11cm3 molecule􀀀1s􀀀1 at the room temperature (namely 298 K), agreeing with the previously reported experimental values. Finally, based on the present calculations, a probable dynamics mechanism was discussed, where the produced HCHO molecule was proposed to be in a vibrationally excited state. This needs further experimental and theoretical observation in the future.<br>

scholarly journals Role of Electronic Excited State in Kinetics of the CH2OO + SO2 ! HCHO + SO3 Reaction

2021 ◽  
Author(s):  
Qingfei Song ◽  
Qiuyu Zhang ◽  
Qingyong Meng
Keyword(s):  
Excited State ◽  
Room Temperature ◽  
Energy Surface ◽  
Regression Method ◽  
Vibrationally Excited ◽  
Compute Data ◽  
Ring Polymer ◽  
Experimental Values ◽  
Kinetics Of

In this work, kinetics of the CH2OO + SO2 ! HCHO + SO3 reaction was studied by ring-polymer molecular dynamics (RPMD). To perform RPMD calculations, multi-reference configuration interaction (MRCI) was first carried out to compute data for constructing potential energy surface (PES) through a kernel regression method. On the basis of the present MRCI calculations, the statics multi-state mechanism involving the lowest-lying singlet excited state (denoted by S 1) was proposed, which is di?erent from the previously proposed mechanism with the lowest-lying triplet state (denoted by T1). Moreover, the present RPMD calculations predicted the rate coe?cient of 3:95?10􀀀11cm3 molecule􀀀1s􀀀1 at the room temperature (namely 298 K), agreeing with the previously reported experimental values. Finally, based on the present calculations, a probable dynamics mechanism was discussed, where the produced HCHO molecule was proposed to be in a vibrationally excited state. This needs further experimental and theoretical observation in the future.<br>

Dynamic adjustment of emission from both singlets and triplets: the role of excited state conformation relaxation and charge transfer in phenothiazine derivates

2021 ◽  
Author(s):  
Weidong Qiu ◽  
Xinyi Cai ◽  
Mengke Li ◽  
Liangying Wang ◽  
Yanmei He ◽  
...  
Keyword(s):  
Excited State ◽  
Charge Transfer ◽  
Intramolecular Charge Transfer ◽  
Dynamic Adjustment ◽  
Twisted Intramolecular Charge Transfer

Dynamic adjustment of emission behaviours by controlling the extent of twisted intramolecular charge transfer character in excited state.

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 Revealing the role of excited state proton transfer (ESPT) in excited state hydrogen transfer (ESHT): systematic study in phenol–(NH3)n clusters

2021 ◽  
Author(s):  
Christophe Jouvet ◽  
Mitsuhiko Miyazaki ◽  
Masaaki Fujii
Keyword(s):  
Excited State ◽  
Proton Transfer ◽  
Systematic Study ◽  
General Model ◽  
Hydrogen Transfer ◽  
Excited State Proton Transfer

A general model of excited state hydrogen transfer (ESHT) which unifies ESHT and the excited state proton transfer (ESPT) is presented from experimental and theoretical works on phenol–(NH3)n. The hidden role of ESPT is revealed.

The role of conformational heterogeneity in the excited state dynamics of linked diketopyrrolopyrrole dimers

2021 ◽  
Author(s):  
Siobhan Bradley ◽  
Ming Chi ◽  
Jonathan White ◽  
Christopher R. Hall ◽  
Lars Goerigk ◽  
...  
Keyword(s):  
Excited State ◽  
Conformational Heterogeneity ◽  
Singlet Fission ◽  
Excited State Dynamics

Diketopyrrolopyrrole (DPP) derivatives have been proposed for both singlet fission and energy upconversion as they meet the energetic requirements and exhibit superior photostability compared to many other chromophores. In this...

scholarly journals Gas phase formation of c-SiC3molecules in the circumstellar envelope of carbon stars

2019 ◽  
Vol 116 (29) ◽  
pp. 14471-14478 ◽  
Author(s):  
Tao Yang ◽  
Luke Bertels ◽  
Beni B. Dangi ◽  
Xiaohu Li ◽  
Martin Head-Gordon ◽  
...  
Keyword(s):  
Carbon Star ◽  
Asymptotic Giant Branch ◽  
Formation Mechanisms ◽  
Circumstellar Envelope ◽  
Outer Envelope ◽  
Parent Molecule ◽  
Silicon Carbon ◽  
Electronically Excited ◽  
Circumstellar Environments ◽  
A Chain

Complex organosilicon molecules are ubiquitous in the circumstellar envelope of the asymptotic giant branch (AGB) star IRC+10216, but their formation mechanisms have remained largely elusive until now. These processes are of fundamental importance in initiating a chain of chemical reactions leading eventually to the formation of organosilicon molecules—among them key precursors to silicon carbide grains—in the circumstellar shell contributing critically to the galactic carbon and silicon budgets with up to 80% of the ejected materials infused into the interstellar medium. Here we demonstrate via a combined experimental, computational, and modeling study that distinct chemistries in the inner and outer envelope of a carbon star can lead to the synthesis of circumstellar silicon tricarbide (c-SiC3) as observed in the circumstellar envelope of IRC+10216. Bimolecular reactions of electronically excited silicon atoms (Si(1D)) with allene (H2CCCH2) and methylacetylene (CH3CCH) initiate the formation of SiC3H2molecules in the inner envelope. Driven by the stellar wind to the outer envelope, subsequent photodissociation of the SiC3H2parent operates the synthesis of the c-SiC3daughter species via dehydrogenation. The facile route to silicon tricarbide via a single neutral–neutral reaction to a hydrogenated parent molecule followed by photochemical processing of this transient to a bare silicon–carbon molecule presents evidence for a shift in currently accepted views of the circumstellar organosilicon chemistry, and provides an explanation for the previously elusive origin of circumstellar organosilicon molecules that can be synthesized in carbon-rich, circumstellar environments.

Role of Solvent in Excited-State Proton Transfer in Hypericin

1994 ◽  
Vol 98 (34) ◽  
pp. 8352-8358 ◽  
Author(s):  
F. Gai ◽  
M. J. Fehr ◽  
J. W. Petrich
Keyword(s):  
Excited State ◽  
Proton Transfer ◽  
Excited State Proton Transfer ◽  
Role Of Solvent
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