The photochemistry of bromine-containing molecules is important for the composition of the atmosphere. When exposed to UV light from the sun, they can decay into free Br atoms which may react with ozone (O3) leading to a reduction in the ozone layer which protects living organisms from excessive solar UV exposure. Carbon tetrahalides such as CBr4 are found in the atmosphere and they constitute an important source of reactive halogens. Their photochemistry in the gas and condensed phase has therefore become an area of active investigation [1].

Studies of the photodissociation of tetrabromomethane by time-resolved optical and X-ray absorption spectroscopy have led to contradictory results in the past. None gave a complete and satisfactory description. Therefore the photochemistry of CBr4 in solution was investigated by time-resolved X-ray diffraction. This method offers the advantage that the scattered X-rays probe all interatomic distances in the sample, implying that all reaction intermediates are probed to within the experimental resolution. This is in stark contranerto optical ne (O3[1].

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