The spectroscopy and photodissociation dynamics of the NCN radical have bee
n investigated by fast beam photofragment translational spectroscopy. The (
B) over tilde (3)Sigma(u)(-)<-- (X) over tilde (3)Sigma(g)(-), (c) over til
de (1)Pi(u)<--(a) over tilde (1)Delta(g), and (d) over tilde (1)Delta(u)<--
(a) over tilde (1)Delta(g) transitions were examined. The major dissociatio
n products for the (B) over tilde (3)Sigma(u)(-) and (c) over tilde (1)Pi(u
) states are N-2((X) over tilde (1)Sigma(g)(+))+C(P-3), while the (d) over
tilde (1)Delta(u) state dissociates to N-2((X) over tilde (1)Sigma(g)(+))+C
(D-1). The dissociation channel, N(S-4)+CN((X) over tilde (2)Sigma(+)) is o
bserved for the (B) over tilde (3)Sigma(u)(-) state at photon energies grea
ter than 4.9 eV, where it comprises approximate to 25 +/- 10% of the total
signal. At all photon energies, the photofragment translational energy dist
ributions show a resolved progression corresponding to the vibrational exci
tation of the N-2 photofragment. The rotational distributions of the molecu
lar fragments suggest that the dissociation pathway for the N-2 loss channe
l involves a bent transition state while the N+CN photofragments are produc
ed via a linear dissociation mechanism. The P(E-T) distributions provide bo
nd dissociation energies of 2.54 +/- 0.030 and 4.56 +/- 0.040 eV for the N-
2 and CN loss channels, respectively, yielding Delta H-f,H-0 K(NCN)=4.83 +/
- 0.030 eV. (C) 1999 American Institute of Physics. [S0021-9606(99)00535-8]
.