The absolute photoabsorption cross-section of pyrrole has been measured bet
ween the ionisation threshold and 35 eV using a double ion chamber and mono
chromated synchrotron radiation. An interpretation has been proposed for so
me of the observed structure in terms of Rydberg series converging onto the
(A) over tilde B-2(1) state threshold. In addition, the possibility that s
everal broad features may be attributed to pi --> pi* transitions is discus
sed. Time-of-flight mass spectra have been recorded for excitation energies
between 11.8 and 77.5 eV, and appearance energies have been determined for
seventeen fragment ions and the doubly charged parent ion. These have enab
led, previously unknown, heats of formation to be estimated for five ions,
including the doubly charged parent ion. A high resolution mass spectromete
r, equipped with an electron impact ionisation source, has been used in B/E
and B-2/E linked scanning modes to identify reactant/product pairings. Fra
gmentation processes leading to the production of several high intensity fr
agment ions have been modelled using ab initio and semi-empirical methods.
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