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A crossed beam study of 18O(3P)+NO2 and 18O(1D)+NO2: Isotope exchange and O2+NO formation channels
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10.1063/1.4736567
/content/aip/journal/jcp/137/4/10.1063/1.4736567
http://aip.metastore.ingenta.com/content/aip/journal/jcp/137/4/10.1063/1.4736567

Figures

Image of FIG. 1.
FIG. 1.

High resolution time-of-flight spectra for 48NO2 (corresponding to isotope exchange products) at 5 different laboratory angles. Experimental data are plotted as open circles; solid lines are the simulated results using the best-fit COM P(θ) and P(ET) distributions shown in Figure 4.

Image of FIG. 2.
FIG. 2.

Newton diagram for isotope exchange products in the high resolution 18O+NO2 crossed beam experiment. The 0° laboratory angle is defined as the direction of the 18O velocity vector; the laboratory angle of the center of mass is ∼46°. The inner circle corresponds to the 48NO2 peak at ∼200 μs, assigned to O(3P)+NO2 isotope exchange (R3). The outer circle corresponds to the average velocity of the fast shoulder, assigned to O(1D)+NO2 quenching with isotope exchange (R5a). Dotted lines represent laboratory angles at which scattering was sampled.

Image of FIG. 3.
FIG. 3.

Left panel: Comparison of the 18O beam profile and 46NO2 scattering signal (mostly from inelastic scattering that is much more intense than reactive scattering) for experiments using 18O-labeled SO2 photolysis (red) and low resolution 36O2 photolysis (black) as a source of 18O. Right panel: Comparison of the 48NO2 isotope exchange signals from the two experiments; the small 48NO2 peak observable at TOFs < 150 μs for the SO2 photolysis source is a result of multiphoton absorption of SO2 (see Sec. II), and is ignored in the analysis since it is well separated in time from the main peak. Angles indicated are in the laboratory frame. Signals from the experiments using the 36O2 photolysis source (18O, 46NO2, and 48NO2) have been universally scaled by a factor of 0.05 (see text). In the right panel, 48NO2 signal from the experiments using the SO2 photolysis source have been scaled by a factor of 0.5. Note the different y-axis scales.

Image of FIG. 4.
FIG. 4.

(a) COM product angular distributions P(θ), and (b) COM product translational energy distributions P(ET) used to simulate the high resolution 48NO2 TOF data, which is the product of the isotope exchange channels (R3) and (R5a). Solid curves represent the O(3P)+NO2 reaction (R3) and dashed curves represent the O(1D)+NO2 reaction (R5a). Gray shading indicates the range of P(θ)s and P(ET)s that adequately simulated the O(3P)+NO2 data (not shown for the O(1D)+NO2 data; see text).

Image of FIG. 5.
FIG. 5.

Laboratory angular distribution of the 48NO2 product from the reaction 18O(3P)+NO2(R3). Filled squares are the experimental data shown with ± 2σ error bars; the solid line is the simulation of the laboratory data using the best-fit COM P(θ) and P(ET) distributions shown in Figure 4.

Image of FIG. 6.
FIG. 6.

Left panel: Comparison of the 18O beam profile and 46NO2 scattering signal for experiments using SO2 photolysis (red) and low resolution 36O2 photolysis (black) as a source of 18O. Right panel: Comparison of 34O2 signals from the two experiments. All angles indicated are in the laboratory frame, and signals (18O, 46NO2, and 48NO2) from the experiments using the 36O2 photolysis source have been scaled by a factor of 0.08. In the right panel, 34O2 signal from the experiments using the SO2 photolysis source have been scaled by a factor of 0.5. Note the different x- and y-axis scales.

Image of FIG. 7.
FIG. 7.

High resolution time-of-flight spectra for 34O2 from 18O(1D)+NO2 (R4a) at 7 different laboratory angles (open circles). Solid lines are a simulation of the data using the P(θ) and P(ET) distributions shown in Figure 10. The small contribution of 34O2 from 18O(3P)+NO2 (R1a) has been subtracted (see text).

Image of FIG. 8.
FIG. 8.

Laboratory angular distribution of the 34O2 product from the reaction 18O(1D)+NO2. Filled squares are experimental data shown with ± 2σ error bars; the solid line is the simulation of the laboratory data using the best-fit COM P(θ) and P(ET) distributions shown in Figure 10.

Image of FIG. 9.
FIG. 9.

Newton diagram showing the 34O2 products for the high resolution 18O+NO2 crossed beam experiment. The circle represents the COM velocity that corresponds to the 90 μs peak observed in the 20° TOF data. Dotted lines represent laboratory angles at which scattering was sampled.

Image of FIG. 10.
FIG. 10.

Solid lines show the COM (a) P(θ) and (b) P(ET) distributions that best simulate the 34O2 TOF signal from O(1D)+NO2 (R4a) in Figure 7. Gray shading indicates the range of uncertainty in P(θ) and P(ET).

Image of FIG. 11.
FIG. 11.

Comparison of the high-resolution TOF spectrum for m/e 32 (green circles) with the high resolution TOF spectrum for 34O2 (blue circles) at a laboratory angle of 40°. The black line is a simulation of the total 34O2 data (from (R1a) and (R4a)) and the magenta line is a simulation of the contribution of O(3P)+NO2 (R1a) to the 34O2 signal. The broad, slow peak centered around 200 μs in the m/e 32 TOF spectrum (green circles) is a result of dissociative ionization of 48NO2 from (R3) to form 32NO+ in the mass spectrometer and not production of either 32O2 or 32NO from (R4b) (see text).

Tables

Generic image for table
Table I.

Summary of experimental results for the 18O(3P)+NO2 and 18O(1D)+NO2 reactions.

Generic image for table
Table II.

Product energy distributionsa and P(θ) characteristics for the O(3P)+NO2 isotope exchange and O(1D)+NO2→O2+NO reactions.

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/content/aip/journal/jcp/137/4/10.1063/1.4736567
2012-07-24
2014-04-21
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: A crossed beam study of 18O(3P)+NO2 and 18O(1D)+NO2: Isotope exchange and O2+NO formation channels
http://aip.metastore.ingenta.com/content/aip/journal/jcp/137/4/10.1063/1.4736567
10.1063/1.4736567
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