A simple ‘statistical’ approach for fragmentation studies of doubly ionized cytosine, thymine and uracil bases

Abstract

A simple statistical model describing the dissociation of molecular dications into correlated fragment pairs has been developed. This model is based on a combinatory approach in which all possible fragments are enumerated and is refined by taking into account the initial structure of the parent molecule, considering the number of chemical bonds to be broken to give rise to the fragments. We show how this model can be used as a tool to help interpreting experimental results of coincidence experiments. It shows that dissociation of doubly ionized molecules upon 100 keV proton irradiation is dominated by statistical processes but it also enables an easy identification of the dissociation products originating from non-statistical processes requiring further investigation, possibly conveying information on the radiation-molecule interaction itself.

Fragmentation of adenine and uracyl molecules through electron captures in collisions with ions

“…It was assumed that capture with ionization takes place within internuclear spacings for which the population of Ar 4+ ** autoionization states is classi cally allowed. The second ionization potential (IP) of an uracyl molecule, which must also be known to determine the range of internuclear spacings, was cal culated to be 17.3 eV [26] and 25.4 eV [17]. For the IPs from [26], we found ratio / = 43/14 in good agreement with experimental data ( Table 1).…”

“…For example, in the case of ionization by pho tons with energies far exceeding the ionization poten tial [7] (IP Ade = 8.4 eV [2,7], IP Ura = 9.3 eV [2,17]), there exists a high probability of molecular ion forma tion because of the resonance character of photoion ization. This seems to decrease the probability of for mation of undissociated molecular ions (Tables 2, 3).…”

“…In fast collisions, the cross section of direct ion ization is the largest. In earlier works, interaction between protons with different energies and molecules of NA bases were studied [6,[12][13][14][15][16][17] and the absolute cross section of electron capture and that of direct ion ization of adenine, cytosine, thymine, and uracyl interacting with protons falling into the energy range covering the Bragg peak (20-150 keV) were found [14]. In addition, in a number of works [18][19][20][21][22], the fragmentation of NA base molecular ions interacting with multiply charged ions, e.g., C z+ (z = 1-6) and some others, was investigated with the aim to see how the atomic number, charged state, and collision veloc ity of an incident ion influence the fragmentation pat tern.…”

Investigation of the fragmentation of core-ionised deoxyribose: a study as a function of the tautomeric form

“…One of them 17 is a simple statistical approach based on the enumeration of assumed equiprobable pathways of breakage of doubly ionised molecules. The other one 18 is based, like ours, on molecular dynamics simulations.…”

Time-dependent density functional theory molecular dynamics simulation of doubly charged uracil in gas phase

“…[7]). In such experiments, fragmentation results from the relaxation of the excess of electronic energy associated with vacancies created in the different electronic shells of the molecule by the collisional process.…”