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Quantum and classical approaches for rotational relaxation and nonresonant laser alignment of linear molecules: A comparison for CO2 gas in the nonadiabatic regime
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10.1063/1.4705264
/content/aip/journal/jcp/136/18/10.1063/1.4705264
http://aip.metastore.ingenta.com/content/aip/journal/jcp/136/18/10.1063/1.4705264

Figures

Image of FIG. 1.
FIG. 1.

Time dependence of CO2 alignments for a 100 fs pulse of 150 TW/cm2 predicted by the quantum model (red) and re-quantified classical calculation (black).

Image of FIG. 2.
FIG. 2.

Detailed views of the results of Fig. 1 with, from left to right, the alignment peak and the first four revivals.

Image of FIG. 3.
FIG. 3.

Effect of the (100 fs) laser power on the amplitudes and shapes of the alignment pic (a) and (b), and first revival (a′) and (b′). The (requantized) classical (CMDS) and the quantum results are displayed on the left (a) and (a′) and right (b) and (b′) plots, respectively. The curves correspond to laser powers of 25 (green), 50 (blue), 100 (black), and 150 (red) TW/cm2.

Image of FIG. 4.
FIG. 4.

Effect of the (100 fs) laser power on the amplitudes of alignment. In blue (right scale) are values of the “permanent” component ⟨cos[θ(t)]2P. The maximum and the minimum of ⟨cos[θ(t)]2T in the alignment peak and first revival are given (left scale) by the upper and lower results in red, respectively. The symbols are quantum predictions while the lines have been obtained using the (requantized) classical (CMDS) approach.

Image of FIG. 5.
FIG. 5.

Relative populations of the rotational levels J after the extinction of the (100 fs) laser pulse (at t+ = 1 ps) for various laser powers. The symbols and lines are results obtained with the quantum and requantized classical (CMDS) approaches, respectively.

Image of FIG. 6.
FIG. 6.

Average rotational energies just after the (100 fs) laser pulse. The symbols and lines are results obtained with the quantum and requantized classical (CMDS) approaches, respectively.

Image of FIG. 7.
FIG. 7.

Collisional broadening coefficients of pure CO2 isotropic Raman Q(J) lines at 296 K. The ECS results are in red, the values from CMDS in blue, and the experimental values (see text) in black. The insert provides a comparison between ECS predictions for the Q(JM) (●) and Q(J) (o).

Image of FIG. 8.
FIG. 8.

State-to-state rates K JJ′ ≠ J for J changes in pure CO2 at 296 K. Classical (CMDS) and quantum (ECS) results are in blue and red, respectively.

Image of FIG. 9.
FIG. 9.

ECS calculated state-to-state rates K J, MJ′, M for J = 20 (top) and J = 40 (bottom) with J′ = J−2 (left) and J′ = J−10 (right) plotted vs M/J and M′/J′.

Image of FIG. 10.
FIG. 10.

State-to-state rates for inelastic J and M changes (see text). Classical (CMDS) and quantum (ECS) results are in blue and red, respectively.

Image of FIG. 11.
FIG. 11.

Same as Fig. 10 but for elastic reorienting (J conserving, M changing) collisions (see text).

Image of FIG. 12.
FIG. 12.

Time dependence of the alignment induced by a (100 ps) 50 TW/cm2 laser pulse in pure CO2 at 1 atm and 296 K. The classical (CMDS) results are in blue. Those of the quantum (ECS) approach with the M-dependent and M-independent models are in red and black, respectively.

Image of FIG. 13.
FIG. 13.

Detailed views of the results in Fig. 12 for successive revivals of the first and second transients.

Image of FIG. 14.
FIG. 14.

CMDS predicted average rotational (dashed lines) and translational (full lines) energies vs time for pure CO2 at 1 atm and initially at 296 K for 50 (red), 100 (blue), and 150 (black) TW/cm2. The horizontal green lines indicate the asymptotic values calculated from Eq. (17).

Image of FIG. 15.
FIG. 15.

Rotational populations (top) and center of mass velocity distributions (bottom) 3 ps (black), 150 ps (red), and 300 ps (blue) after a (100 ps) 150 TW/cm2 laser pulse in pure CO2 at 1 atm and initially at 296 K. The symbols are CMDS results and the lines correspond to Boltzmann distributions calculated with the rotational and translational temperatures of Fig. 14.

Tables

Generic image for table
Table I.

Time constants (in ps at 1 atm and 296 K) of the exponential decays of the transient amplitudes (τ T) and “permanent” (τ P) components of ⟨cos2[θ(t)]⟩ obtained from the requantized classical approach (CMDS) and the quantum (ECS) model using M-dependent and M-independent state-to-state rates. For comparison (see Appendix D), values of the averaged (using the populations after the pulse) Q(J)and Q(JM) line broadening coefficients are given in the last two columns.

Generic image for table
Table II.

Time constants (in ps at 1 atm) of the exponential decays of the transient amplitudes (τ T) and “permanent” (τ P) components of ⟨cos2[θ(t)]⟩ obtained with the quantum (ECS) model by including or neglecting the effects of reorienting and/or dephasing elastic collisions. Results obtained for CO2 at 1 atm, 296 K, and a (100 fs) pulse of 50 TW/cm2.

Generic image for table
Table III.

Time constants (ps atm) of the exponential decays of the components of the alignment within the M-conserving and M-randomizing models; values obtained from a thermal average (at 296 K) of the broadening coefficient in the insert in Fig. 7.

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/content/aip/journal/jcp/136/18/10.1063/1.4705264
2012-05-09
2014-04-24
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Quantum and classical approaches for rotational relaxation and nonresonant laser alignment of linear molecules: A comparison for CO2 gas in the nonadiabatic regime
http://aip.metastore.ingenta.com/content/aip/journal/jcp/136/18/10.1063/1.4705264
10.1063/1.4705264
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