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Photodissociation of 1-bromo-2-butene, 4-bromo-1-butene, and cyclopropylmethyl bromide at studied using velocity map imaging
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10.1063/1.2353836
/content/aip/journal/jcp/125/14/10.1063/1.2353836
http://aip.metastore.ingenta.com/content/aip/journal/jcp/125/14/10.1063/1.2353836

Figures

Image of FIG. 1.
FIG. 1.

Potential energy surface displaying the dissociation and isomerization channels among the 1-methylallyl, cyclopropylmethyl, 3-buten-1-yl, and cyclobutyl radicals. The values are obtained at the G3//B3LYP level. Note that the ring-opening barrier between cyclobutyl and 3-buten-1-yl radicals was misconnected between cyclobutyl and cyclopropylmethyl radicals in our previous study (Fig. 5 in Ref. 14). The methylene shift barrier between cyclobutyl and cyclopropylmethyl radicals has now been located and included here.

Image of FIG. 2.
FIG. 2.

(Color online) Raw images (a) obtained at and (b) obtained at from the C–Br bond fission of 1-bromo-2-butene. The laser polarization is along the vertical direction in the plane of the images. Each image consists of and is constructed by accumulating signals from laser shots. The distance of on the phosphor screen corresponds to the width of in the images and Br atom recoil velocity.

Image of FIG. 3.
FIG. 3.

The ’s of and derived from Fig. 2.

Image of FIG. 4.
FIG. 4.

(Color online) Raw image of the 1-methylallyl radical from the C–Br bond fission of 1-bromo-2-butene at . There is no noticeable signal at only. Each image has a dimension of .

Image of FIG. 5.
FIG. 5.

(Color online) The C–Br fission derived from the 1-methylallyl radical data in Fig. 4 is shown in solid line. The dashed line shows the best fit C–Br fission obtained from the weighted sum of the individual Br distributions in Fig. 3 (those weighted contributions are shown in dotted and dot-dashed line).

Image of FIG. 6.
FIG. 6.

Angular distribution fitting of (a) 1-methylallyl radical, (b) , and (c) formed in the C–Br bond fission of 1-bromo-2-butene.

Image of FIG. 7.
FIG. 7.

(Color online) Raw images (a) obtained at and (b) obtained at from the C–Br bond fission of cyclopropylmethyl bromide. The laser polarization is along the vertical direction in the plane of the images. Each image consists of and is constructed by accumulating signals from laser shots. The distance of on the phosphor screen corresponds to the width of in the images and Br atom recoil velocity.

Image of FIG. 8.
FIG. 8.

The ’s of and derived from Fig. 7.

Image of FIG. 9.
FIG. 9.

(Color online) Raw images of the cyclopropylmethyl radical from the C–Br bond fission of cyclopropylmethyl bromide (a) at and (b) at . A high-translational energy component appearing in (a) but not in (b) reveals that the contribution of cyclopropylmethyl fragments from 234 photodissociation with the radicals ionized by the photons. Each image has a dimension of .

Image of FIG. 10.
FIG. 10.

(Color online) The of cyclopropylmethyl radical derived from Fig. 9 (shown in solid line). The dashed line is obtained from the weighted sum of the individual Br distributions in Fig. 8 using the line strength ratio determined in this work.

Image of FIG. 11.
FIG. 11.

Angular distribution fitting of (a) cyclopropylmethyl radical, (b) , and (c) formed in the C–Br bond fission of cyclopropylmethyl bromide.

Image of FIG. 12.
FIG. 12.

(Color online) The of cyclobutyl radical is taken from Ref. 14 (shown in solid line). The (dotted line) is obtained from the weighted sum of the individual Br distributions using the newly deduced REMPI line strength factor.

Image of FIG. 13.
FIG. 13.

(Color online) Raw images (a) obtained at and (b) obtained at from the C–Br bond fission of 4-bromo-1-butene. The laser polarization is along the vertical direction in the plane of the images. Each image consists of and is constructed by accumulating signals from laser shots. The distance of on the phosphor screen corresponds to the width of in the images and Br atom recoil velocity.

Image of FIG. 14.
FIG. 14.

The ’s of and derived from Fig. 13.

Image of FIG. 15.
FIG. 15.

(Color online) Raw image of the radical from the C–Br bond fission of 4-bromo-1-butene (a) at and (b) at . A high-translational energy component appearing in (a) but not in (b) reveals that the contribution of fragments from 234 photodissociation and followed by the photoionization. Each image has a dimension of .

Image of FIG. 16.
FIG. 16.

(Color online) The partial C–Br fission shown in solid line is derived from the velocities of the radicals detected using photoionization, shown in Fig. 15. The C–Br fission shown in dashed line is obtained from the weighted sum of the individual Br distributions in Fig. 14 (shown in dotted line and dot-dashed line).

Image of FIG. 17.
FIG. 17.

Angular distribution fitting of (a) and (b) formed in the C–Br bond fission of 4-bromo-1-butene.

Image of FIG. 18.
FIG. 18.

Gas phase ultraviolet absorption spectrum of (a) 1-bromo-2-butene, (b) cyclopropylmethyl bromide, and (c) 4-bromo-1-butene.

Image of FIG. 19.
FIG. 19.

(Color online) Potential energy surface displaying energetics for the dissociation and isomerization channels among the 1-methylallyl, cyclopropylmethyl, 3-buten-1-yl, and cyclobutyl radicals from Fig. 1. The internal energy distributions of the nascent radicals generated in this study are shown by the overlaid curve above the corresponding radicals. Note that the internal energy distribution of the radical are determined from momentum conservation with the detected Br fragments and energy conservation, correcting for the fact that the radicals produced in coincidence with have less internal energy. The contribution shown in red in the online version corresponds to the internal energy distribution of radicals formed with the cofragments and contribution shown in blue in the online version represents the internal energy distribution of radicals formed with the cofragments.

Tables

Generic image for table
Table I.

The bond dissociation energy , initial vibrational energy contents at , and available energy in kcal/mol after photodissociation for each individual precursor.

Generic image for table
Table II.

The adiabatic and vertical IEs (in eV) calculated at the G3//B3LYP level for each individual radical generated in this study.

Generic image for table
Table III.

A summary of the anisotropy parameters for the and channels and the spin-orbit branching ratios obtained in this study.

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/content/aip/journal/jcp/125/14/10.1063/1.2353836
2006-10-11
2014-04-24
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Photodissociation of 1-bromo-2-butene, 4-bromo-1-butene, and cyclopropylmethyl bromide at 234nm studied using velocity map imaging
http://aip.metastore.ingenta.com/content/aip/journal/jcp/125/14/10.1063/1.2353836
10.1063/1.2353836
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