scholarly journals Uv Multiphoton Induced Chemistry of Nitrobenzene in Solution

1990 ◽  
Vol 10 (3) ◽  
pp. 177-184 ◽  
Author(s):  
Joseph J. Belbruno ◽  
Gary Siuzdak ◽  
Simon North
Keyword(s):  
Ground State ◽  
Preliminary Report ◽  
Organic Molecules ◽  
Laser Intensity ◽  
Multiphoton Ionization ◽  
Ionic Species ◽  
Gas Chromatography Mass Spectrometry ◽  
Triplet Level ◽  
Vibrationally Excited ◽  
Ground State Molecule

The technique of Multiphoton Induced Chemistry (MPIC) has been employed to initiate ion-molecule chemistry of organic molecules in solution. We report one of the first examples of the use of liquid phase multiphoton ionization (MPI) to prepare organic cations, which then react with the solvent in ionmolecule processes. The products obtained in this chemical sequence are significantly different from those observed in conventional or multiphoton-induced neutral chemistry in the same solvent. The particular example explored in this work is the reactivity of the nitrobenzene cation in methanol solvent. Products of the ion-molecule chemistry, detected by gas chromatography/mass spectrometry, are phenol and benzyl alcohol. These products depend upon the square of the laser intensity. It is shown by ionization current measurements in a conductance cell, that ionic species are produced as precursors to the observed products. The implications of this application of MPI are briefly discussed. A preliminary report on the unimolecular chemistry of the highly excited neutral molecule is also included. The product of this channel is nitrosobenzene. It is shown, in this case, that the reactive state is most likely a highly vibrationally excited ground state molecule, not the lowest triplet level invoked in conventional photochemistry.

Formation and dissociation of , , and ions by ruby laser radiation

1985 ◽  
Vol 63 (7) ◽  
pp. 976-982 ◽  
Author(s):  
G. S. Wagner ◽  
N. R. Isenor
Keyword(s):  
Laser Radiation ◽  
Experimental Work ◽  
Ground State ◽  
Ruby Laser ◽  
Multiphoton Ionization ◽  
Ionic Species ◽  
Laser Polarization ◽  
Dissociation Energies ◽  
Direct Measurements ◽  
State Dissociation

Multiphoton ionization of K2, Rb2, and Cs2 in beam conditions by pulsed ruby laser radiation (λ = 6946.0 Å, pulse duration ~10 ns) and subsequent dissociation of the dimer ions by one or more additional photons have been observed. Ground-state dissociation energies of these ionic species have been determined directly from the time of flight of the dissociation fragment pairs, and from the use of retarding potentials, to be [Formula: see text], [Formula: see text], and [Formula: see text]. These observed values have been compared with the theoretical and experimental work of other authors. Our results for the [Formula: see text] and [Formula: see text] ions are the first direct measurements of their ground-state dissociation energies. The effect of laser polarization on the dissociation mechanism has also been experimentally investigated.

Photochemical studies of unimolecular processes I. The photoisomerization of cycloheptatriene and cycloheptatriene-d 8

1970 ◽  
Vol 316 (1524) ◽  
pp. 123-130 ◽  
Keyword(s):  
Ground State ◽  
Vibrationally Excited ◽  
Parent Molecule ◽  
Photochemical Isomerization ◽  
Ground State Molecule

The photochemical isomerization of cyclo [1. 3. 5] heptatriene to toluene was studied at seven wavelengths between 228.8 and 313.0 nm. It was shown to occur via a vibrationally excited ground state molecule, the isomerization being quenched by added gases (the parent molecule, toluene, SF 6 , CO 2 , He) according to the Stern-Volmer law. The perdeuteriated compound was also studied.

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>

Ultraviolet photodissociation dynamics of PCl3 at 235 nm: three-dimensional ion imaging and theoretical analysis

2021 ◽  
Author(s):  
Alexei Chichinin ◽  
Christof Maul ◽  
Karl-Heinz Gericke
Keyword(s):  
Theoretical Analysis ◽  
Ground State ◽  
Multiphoton Ionization ◽  
Three Dimensional ◽  
Ion Imaging ◽  
Ultraviolet Photodissociation

The photodissociation dynamics of PCl3 at 235 nm has been studied by monitoring ground state Cl(2P3/2) and spin-orbitally excited Cl(2P1/2) atoms by resonance enhanced multiphoton ionization(REMPI). Also, the PCl+n (n=0,1,2)...

scholarly journals The Microwave Spectrum of 3,4-Dihydro-1,2-Pyran

1985 ◽  
Vol 40 (9) ◽  
pp. 913-919
Author(s):  
Juan Carlos López ◽  
José L. Alonso
Keyword(s):  
Dipole Moment ◽  
Excited States ◽  
Ground State ◽  
Principal Axis ◽  
Microwave Spectrum ◽  
Average Intensity ◽  
Ring Conformation ◽  
Vibrationally Excited ◽  
Rotational Constants ◽  
Displacement Measurements

Abstract The rotational transitions of 3,4-dihydro-1,2-pyran in the ground state and six vibrationally excited states have been assigned. The rotational constants for the ground state (A = 5198.1847(24), B = 4747.8716(24) and C = 2710.9161(24) have been derived by fitting μa, μb and μc-type transitions. The dipole moment was determined from Stark displacement measurements to be 1.400(8) D with its principal axis components |μa| =1.240(2), |μb| = 0.588(10) and |μc| = 0.278(8) D. A model calculation to reproduce the ground state rotational constants indicates that the data are consistent with a twisted ring conformation. The average intensity ratio gives vibrational separations between the ground and excited states of the ring-bending and ring-twisting modes of ~ 178 and ~ 277 cm-1 respectively.

The Dielectric Discharge as an Efficient Generator of Active Nitrogen for Chemiluminescence and Analysis

1983 ◽  
Vol 37 (6) ◽  
pp. 545-552 ◽  
Author(s):  
John Kishman ◽  
Eric Barish ◽  
Ralph Allen
Keyword(s):  
Gas Phase ◽  
Ground State ◽  
Band System ◽  
Electrothermal Atomization ◽  
Characteristic Radiation ◽  
Gaseous Species ◽  
Vibrationally Excited ◽  
Active Nitrogen ◽  
Excited Species ◽  
Intense Emission

A predominantly blue “active nitrogen” afterglow was generated in pure flowing nitrogen or in air by using a dielectric discharge at pressures from 1 to 20 Torr. The afterglow contains triplet state molecules and vibrationally excited ground state molecules. These species are produced directly by electron impact without the formation and recombination of nitrogen atoms. The most intense emission is the N2 second positive band system. The N2 first positive and N2+ first negative systems are also observed. The spectral and electrical properties of this discharge are discussed in order to establish guidelines for the analytical use of the afterglow for chemiluminescence reactions. The metastatic nitrogen efficiently transfers its energy to atomic and molecular species which are introduced into the gas phase and these excited species emit characteristic radiation. The effects of electrothermal atomization of Zn and the introduction of gaseous species (e.g., NO) on the afterglow are described.

Emerging investigators series: silica-crosslinked graphene oxide membrane and its unique capability in removing neutral organic molecules from water

2016 ◽  
Vol 2 (4) ◽  
pp. 717-725 ◽  
Author(s):  
Sunxiang Zheng ◽  
Baoxia Mi
Keyword(s):  
Graphene Oxide ◽  
Organic Molecules ◽  
Ionic Species ◽  
Oxide Membrane ◽  
Unique Capability

A new graphene oxide (GO) membrane was synthesized by crosslinking GO nanosheets via silica. This membrane was found to remove neutral organic molecules much more efficiently than negatively charged ionic species.

Preferred Rotameric Conformations of Isobutyraldehyde, Their Dipole Moments and Vibrationally Excited States by Microwave Spectroscopy

1986 ◽  
Vol 41 (3) ◽  
pp. 483-490 ◽  
Author(s):  
O. L. Stiefvater
Keyword(s):  
Oxygen Atom ◽  
Excited States ◽  
Ground State ◽  
Dipole Moments ◽  
Microwave Spectroscopy ◽  
Centrifugal Distortion ◽  
Gauche Conformation ◽  
Vibrationally Excited ◽  
Trans Conformation ◽  
Centrifugal Distortion Constants

The earlier prediction of the preferred and the less stable rotameric conformations of isobutyraldehyde, (CH3)2CHCHO, has been confirmed experimentally by microwave spectroscopy. The compound exists mainly in a gauche conformation, in which one of the methyl groups is eclipsed by the oxygen atom, and the less stable rotamer is the trans conformation, in which the oxygen atom eclipses the isopropyl hydrogen.Ground state rotational constants (in MHz) and centrifugal distortion constants (in kHz), together with dipole moments (in D), are:Rotation spectra due to three torsionally excited states of each rotamer have been identified, along with satellites arising from CH3 internal rotation and CC2 wagging.

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