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Photodissociation of carbon dioxide in singlet valence electronic states. II. Five state absorption spectrum and vibronic assignment
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10.1063/1.4808370
/content/aip/journal/jcp/138/22/10.1063/1.4808370
http://aip.metastore.ingenta.com/content/aip/journal/jcp/138/22/10.1063/1.4808370
View: Figures

Figures

Image of FIG. 1.
FIG. 1.

(a) Experimental absorption cross section of CO ( = 195 K; in cm) as a function of photon energy (in 10 cm). Numbers on the cross section axis denote powers of ten. The photon energy range studied in this work is indicated with two dashed lines. (b) Absorption spectrum, calculated at = 200 K (blue line, vertically shifted by 0.9 × 10 cm), compared with the experimental spectrum (black line). Electronic assignment in terms of adiabatic states is given. Experimental data are from Ref. . Theoretical spectrum is shifted by 400 cm to lower energies.

Image of FIG. 2.
FIG. 2.

Cuts through the PESs of the adiabatic states along (a) OCO angle (fixed coordinates are = 2.2  and = 2.3  ) and (b) one CO bond distance (fixed coordinates are = 2.3  and α = 175°). The thick black line in both panels is the ground electronic state ; excited ′ and ′′ states are shown with thin black and brown lines, respectively. Red lines and arrows illustrate the non-vertical excitation process and the effect of the TDM on the initial vibrational wave function ψ in . ψ is shown in both panels with a dashed line, and the shapes of the initial state in the optical transitions via and components of the TDM, μψ (a) and μψ (b) are shown with solid lines. Arrows, indicating excitations, pass through the maximum of ψ and the maxima of μψ and μψ.

Image of FIG. 3.
FIG. 3.

Spatial components μ (a) and (d), μ (b) and (e), and μ (c) and (f) of the TDM vectors for the adiabatic states 2 ′ (purple), 3 ′ (brown), 1 ′′ (black), 2 ′′ (purple), and 3 ′′ (brown) from the ground state . ′ states are shown with solid, ′′ states with open symbols. Dependences on the CO bond distance are shown in (a)–(c) [fixed coordinates are = 2.2  and α = 179°] and dependences on the OCO angle are shown in (d)–(f) [fixed coordinates are = 2.2  and = 2.3  ]. TDMs are measured in atomic units. The coordinate axes are sketched in (b): is directed along the molecular figure axis, and is normal to in the molecular plane, and is normal to the molecular plane.

Image of FIG. 4.
FIG. 4.

(a) The absorption spectrum σ( | = 0) for a single initial state = 0 (blue) compared with the spectrum of Ref. measured at = 195 K (black). Thin sticks indicate the major experimental peaks separated into a strong (brown) and a weak (blue) progression in the high energy band, and a strong progression in the low energy band (black). Their positions are taken from Table X of Ref. augmented with data from Ref. . Panels (b)–(d) show decomposition of the calculated spectrum and vibronic assignments: (b) σ( | = 0) spectrum (thin gray line) broken down into two low resolution components stemming from excitations of the bent (2 ′, 1 ′′, thick black line) and linear (3 ′, 3 ′′, thick blue line) adiabatic states. Two spectra at the bottom are the parallel (σ, thick green line) and the perpendicular (σ, thick red line) components of σ( | = 0). (c) Decomposition of σ (green) in terms of resonance states of the Hamiltonian Eq. (11) . Gray sticks mark resonance positions (every 3d calculated state is shown). Black line is the sum of Lorentzians in Eq. (16) . (d) Vibronic assignment of σ (green) in terms of the most intense resonances shown at the bottom of the panel with thin sticks. Vertical shift of the calculated spectra is 0.9 × 10 cm in panels (a) and (b), and 0.6 × 10 cm in panels (c) and (d).

Image of FIG. 5.
FIG. 5.

Left and right columns depict 3′ adiabatic components of the 3D wave functions of resonance states in progressions ( , 0, 0) and ( , 0, 1), respectively. The probability density distribution is projected onto the ( , ) plane. Shaded black indicates regions of high density. Middle column depicts eigenstates ψ( , ) calculated in the 2D single state model. All states belong to progression ( , 0); red contours represent positive, blue contours negative values of ψ. In all panels, a 2D contour map of the 3′ adiabatic potential for α = 179° (gray lines) and the CI seam (black thick line) are sketched. Axis tic labels are in . States marked are mixed with states shown in Fig. 6 . The top middle panel shows author's drawing of a Mongolian hat.

Image of FIG. 6.
FIG. 6.

(Upper panels) 3′ adiabatic components of the 3D wave functions of resonance states in the progression ( , 1, 0). The state (3, 1, 0) could not be found. Lower panels depict eigenstates ψ( , ) calculated in the 2D single state model and belonging to the progression ( , 1). The layout of all wave functions is the same as in Fig. 5 . The 2D states are mixed with states ( + 4, 0); counterparts of those marked are shown in Fig. 5 .

Image of FIG. 7.
FIG. 7.

(Upper panels) Frequencies (a) in the major experimental progression, (b) in the progression ( , 0, 0) in the full calculations, and (c) in the progression ( , 0) in the 2D model. In (b), frequencies are lifted by 50 cm; in (c), the frequency scale is omitted. Arrows emphasize the positions of dips in the progressions. (Lower panels) Potential of the 3 ′ state (d) at α = 179° along the CI seam and (e) across the Mongolian hat top. Angular coordinate ϕ along the seam in (d) is chosen such that ϕ = 180° for = = 2.24  ; the “radial” coordinate in (e) runs along the antisymmetric stretch , and the origin = 0 is the point = = 2.5  . Potential curves are raised through the zero point energies of “missing” coordinates, ℏω/2 and ℏω/2 in (d) and (e), respectively. Vibrational ladder in the 2D model is indicated in (d) and (e). Energy spacings forming two dips in the progression in panel (c) are highlighted with gray and yellow.

Image of FIG. 8.
FIG. 8.

Shown left of the vertical dashed line are frequencies in the pure progressions of eigenstates in which the 2 ′ adiabatic component (purple, blue, and brown lines and symbols) or the 1 ′′ adiabatic component (red lines and symbols) are most populated. Open black symbols are the two experimental vibrational progressions (triangles and squares), as well as the frequency shift between their band maxima (circles) taken from Table 3 of Ref. . Shown right of the vertical dashed line are energy intervals between adjacent diffuse peaks in the experimental spectrum of Ref. (black open circles) and between most intense resonance states (green solid circles). Note that the frequency scale changes in the upper part of the figure.

Image of FIG. 9.
FIG. 9.

2′ adiabatic component of the resonance state with = 8.3795 eV and Γ = 62 cm. The probability density distribution is projected onto the ( , ) plane in the left panel and onto the (α, ) plane in the right panel. Shaded black indicates regions of high density. The 2D contour maps of the 2 ′ adiabatic potential in the ( , ) plane and in the (α, ) plane are sketched in the left and right panels, respectively. Thick black lines trace out the probability density buildup away from the linear FC region.

Image of FIG. 10.
FIG. 10.

2′ adiabatic components of the 3D wave functions of states in the progression ( , 0, 0) (upper panels) and (0, 0, ) (lower panels) shown against the 2D contour maps of the 2 ′ adiabatic potential in the ( , ) plane.

Image of FIG. 11.
FIG. 11.

2′ adiabatic components of the 3D wave functions of states in the progression (0, , 0) shown against the 2D contour maps of the 2 ′ adiabatic potential in the (α, ) plane. In the left lower frame, the ground vibrational state in the carbene-type OCO minimum is shown and labeled (0, 0, 0).

Image of FIG. 12.
FIG. 12.

Absorption spectrum of the state and assignments of the three progressions ( , 0, ) in which the most intense absorption lines are found.

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/content/aip/journal/jcp/138/22/10.1063/1.4808370
2013-06-12
2014-04-19
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Photodissociation of carbon dioxide in singlet valence electronic states. II. Five state absorption spectrum and vibronic assignment
http://aip.metastore.ingenta.com/content/aip/journal/jcp/138/22/10.1063/1.4808370
10.1063/1.4808370
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