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Full-dimensional quantum dynamics of vibrationally highly excited
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Image of FIG. 1.
FIG. 1.

Graphical definition of Radau coordinates for ammonia and isotopologues (see discussion in the text).

Image of FIG. 2.
FIG. 2.

Coherent absorption spectrum in the region of the NH stretching fundamental; , 6D calculations using the MCTDH code and based on the AMMPOT4 PES. Peaks labeled A–E are discussed in the text. (– – –) and (——) .

Image of FIG. 3.
FIG. 3.

Time evolution of the population of R-type molecules (reactant population evolution), according to Eq. (17), during excitation with a time averaged intensity at three different excitation wave numbers corresponding to peaks A, B, and C in Fig. 2. After 2 ps, two lines are shown for each excitation wave number, indicating evolutions at laser on/off conditions as follows: (A) , laser on (- - -), off (◇-◇); (B) , laser on (——), off (--); (C) , laser on (– –), off (○ –○).

Image of FIG. 4.
FIG. 4.

Time evolution of the absorbed energy, Eq. (15), six-dimensional calculations; peaks A, B, and C as defined in Fig. 2. The horizontal, dashed, and dotted line indicates the classical barrier energy ( on AMMPOT4) (Ref. 32). (- - -) (peak A), (——) (peak B), and (– – –) (peak C).

Image of FIG. 5.
FIG. 5.

Snapshots of the time dependent reduced probability densities (upper row) and (lower row) [see Eq. (18)] after 100 fs of excitation at and . Probability densities are represented by broad isodensity contour lines, drawn at monotonically darkening gray tones; the outermost lines give the lowest densities at (upper row) and (lower row), and all following lines are at constant increments of (upper row) and (lower row). Because of their width, contour lines become indistinguishable at higher densities, which are then indicated by the darkness of the region. Probability density contours are superimposed to 12 thin contour lines of sections of the potential energy surface AMMPOT4 (Ref. 32), ranging from 500 to , at increments of . Sections were calculated at equilibrium values of the remaining coordinates: , (upper row), , , and (lower row). Straight interrupted lines show key coordinate values (see also text).

Image of FIG. 6.
FIG. 6.

Snapshots of the time dependent reduced probability densities (upper row) and (lower row) after 1238 fs of excitation at and (see also Fig. 5).

Image of FIG. 7.
FIG. 7.

Graphical representation of the laser induced stereomutation process at (pathway B); indicated are the section of the PES along the coordinate at equilibrium values for the remaining coordinates (see Fig. 5), the positions of spectroscopic states participating most importantly at the dynamics (with continuous, horizontal lines; see also Table I), and the reduced, 1D probability densities corresponding to the initial state and to the spectroscopic state at . Dashed horizontal lines and vertical arrows indicate the one- and two-photon resonance levels.

Image of FIG. 8.
FIG. 8.

Time evolution of populations of spectroscopic states, Eq. (19), during excitation at (column B) and (column C), and ; continuous lines are states of positive, interrupted lines are states of negative inversion parity. (a) Ground state doublet: (—) and (– – –) . (b) doublet: (– – –) and (—) . (c) doublet: (– – –) and (—) . (d) doublet: (—) and (– – –) .

Image of FIG. 9.
FIG. 9.

Reactant population evolution, according to Eq. (17), but in the 4D model described in Sec. ???, during excitation at ; excitation wave numbers differ slightly for the two PES representations compared here (see text): (– – –) AMMPOT 1 , (—) AMMPOT4 , and (- - -) AMMPOT4 (, 6D calculation as in Fig. 3).

Image of FIG. 10.
FIG. 10.

Time evolution of state vector components , as obtained with MCTDH (left hand side) and URIMIR (right hand side), at and , for AMMPOT1. Continuous lines are states of positive, interrupted lines are states of negative inversion parity. (a) Population of ground state doublet: (—) and (– – –) . (b) Population of an excited doublet: (– – –) and (—) . (c) Relative phases of the excited doublet [line code as under (b)] (see text for definitions).


Generic image for table
Generic image for table
Table I.

Experimental and calculated vibrational wavenumbers for . In Ref. 32 a complete list of theoretical term values to up to is given.

Generic image for table
Table II.

Run time parameters for MCTDH.


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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Full-dimensional quantum dynamics of vibrationally highly excited NHD2