Photodissociation of ClN(3) at 157 nm: Theory suggests a pathway leading to cyclic N(3).
The photodissociation dynamics of chlorine azide (ClN(3)) at the 157 nm region was studied theoretically using the multireference configuration interaction method and the complete active space self-consistent field direct dynamics method. The excitation at the 157 nm region was assigned to the 4 (1)A(')(S(7))<--X (1)A(')(S(0)) transition. A likely pathway for the formation of cyclic N(3) after this transition was identified by direct dynamics as follows: ClN(3) excited to 4 (1)A(')(S(7)) dissociates after about 40 fs to excited N(3)(2 (2)A('), with about 44 kcal/mol internal energy) +Cl((2)P). This vibrationally hot N(3)(2 (2)A(')) goes diabatically through a conical intersection with N(3)(1 (2)A(')) at 44 fs onto 1 (2)A('). At 19 fs later and repeatedly after every 55 fs, N(3)(1 (2)A(')) crosses and trickles down via Coriolis coupling to N(3)(2 (2)A(")/ (2)B(1)) state, which has a potential minimum at the cyclic-N(3) structure. Some fraction of N(3)(2 (2)A(")/ (2)B(1)) produced will survive dissociation and will be found as the cyclic N(3), and some other fraction will eventually dissociate to N((2)D)+N(2) over a high barrier found previously.
Kerkines
Ioannis S K
IS
Cherry L. Emerson Center for Scientific Computation and Department of Chemistry, Emory University, 1515 Dickey Drive, Atlanta, Georgia 30322, USA.
Wang
Zhi
Z
Zhang
Peng
P
Morokuma
Keiji
K