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Negative ions of p-nitroaniline: Photodetachment, collisions, and ab initio calculations
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10.1063/1.4810869
/content/aip/journal/jcp/138/23/10.1063/1.4810869
http://aip.metastore.ingenta.com/content/aip/journal/jcp/138/23/10.1063/1.4810869

Figures

Image of FIG. 1.
FIG. 1.

Stick diagram of the p-nitroaniline molecule showing the donor (NH) and acceptor (NO) moieties responsible for the large dipole moment of this molecule.

Image of FIG. 2.
FIG. 2.

Schematic of the CID apparatus (QStar Elite TOFMS) showing the quadrupole Q1 for isolation of the electrospray ions and the collision region containing argon gas (CAD) followed by product ion identification by the TOF Mass Spectrometer. Differential pumping occurs at each chamber as shown along with approximate operating pressures in each region.

Image of FIG. 3.
FIG. 3.

The photoelectron spectrum of the valence p-nitroaniline anion recorded at 2.54 eV photons. The EA is estimated as the signal onset at 0.75 ± 0.1 eV and a VDE of 1.1 eV.

Image of FIG. 4.
FIG. 4.

Appearance of fragments caused by collision of [NA-H] with argon at lab frame energies of 9 eV, 12 eV, and 17 eV. Relative abundances are normalized to the parent anion peak.

Image of FIG. 5.
FIG. 5.

Nonlinear fits of the CID cross-section of [NA-H] into (a) [NA-H-NO] and (b) NO .

Image of FIG. 6.
FIG. 6.

Natural orbitals from EA-EOM-CCSD/Aug-cc-pVDZ+ calculations for the two lowest states of the NA anion. At the C symmetrical transition state the two lower states of the anion have different symmetries, A and B. Therefore, they are completely decoupled, and can be characterized as dipole-bound and valence. (a) shows the 80% enclosing iso-surface of the dipole-bound state and (b) shows the 90% enclosing iso-surface of the valence state. Note the different length scale of the two figures; ⟨|r|⟩ is 8.5 Å for the natural orbital of the dipole-bound state and just 2.6 Ǻ for that of the valence state.

Image of FIG. 7.
FIG. 7.

Natural orbitals from EA-EOM-CCSD/Aug-cc-pVDZ+ calculations for the two lowest states of the NA anion. At the C symmetrical minimal energy geometry, the two lower states of the anion both have A symmetry are strongly coupled, and can not consequently be characterized as either dipole-bound or valence. Eighty-percent enclosing iso-surfaces of the first and second states are shown in (a) and (b), respectively. Note the comparable length scale of the two figures; ⟨|r|⟩ of the respective natural orbital is 4.3 Å for the lower and 6.8 Å for the higher state.

Image of FIG. 8.
FIG. 8.

A compilation of experimental electron binding energies versus molecular dipole moment. There is some uncertainty as to the dipole moment of the isolated NA molecule; however, it has been measured in acetone to be 6.2 D.

Tables

Generic image for table
Table I.

Dissociation barrier energies of [NA-H]. Calculated energies are the difference between deprotonated NA and the transition state.

Generic image for table
Table II.

Vertical electron affinities, in meV, computed with the EA-EOM-CCSD method. The standard augmented double-ζ and triple-ζ basis set were further augmented with a 666 set of extra diffuse functions at the center of mass of the molecule. At the C symmetric transition state dipole-bound states have A symmetry while the valence state has B symmetry. In C symmetry all bound states have A symmetry, and only the third state can be characterized as dipole-bound, whereas the lower two states show a mixed character.

Generic image for table
Table III.

Vertical detachment energy, in eV, computed with different methods and basis sets. Two geometries are considered, the C symmetrical minimal energy structure of the NA anion, and the associated C symmetrical transition state of the NH inversion.

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/content/aip/journal/jcp/138/23/10.1063/1.4810869
2013-06-19
2014-04-24
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Negative ions of p-nitroaniline: Photodetachment, collisions, and ab initio calculations
http://aip.metastore.ingenta.com/content/aip/journal/jcp/138/23/10.1063/1.4810869
10.1063/1.4810869
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