화학공학소재연구정보센터
Journal of Chemical Physics, Vol.117, No.3, 1040-1046, 2002
Photofragment emission yield spectroscopy of acetylene in the (D)over-tilde (1)Pi(u), (E)over-tilde (1)A, and (F)over-tilde (1)Sigma(+)(u) states by vacuum ultraviolet and infrared vacuum ultraviolet double-resonance laser excitations
The excitation spectra of the (D) over tilde (1)Pi(u), (E) over tilde (1)A, and (F) over tilde (1)Sigma(u)(+) states of C2H2 in the 135.3-130.8 nm range are measured under jet-cooled conditions by detecting fluorescence emitted from C2H((A) over tilde (2)Pi) or C2H((B) over tilde (2)A(')) photofragments. In the photofragment emission yield spectra, the origin bands of the (D) over tilde-(X) over tilde and (F) over tilde-(X) over tilde transitions are observed with Lorentzian profiles with bandwidth (Gamma) of 58.9(4) and 66.7(2) cm(-1), respectively. By identifying the bending progressions of the (E) over tilde-(X) over tilde transition appearing with narrower Lorentzian profiles with, Gammasimilar to40 cm(-1), the band previously considered to be the origin band of the (E) over tilde-(X) over tilde transition is assigned to the transition to the second overtone (v(3)=3) level in the near-cis bending (nu(3)) mode. The transitions to the C-H stretch excited levels in the (D) over tilde and (F) over tilde states are observed using the infrared-VUV double resonance excitation scheme. The (D) over tilde 3(1)(1), (D) over tilde 1(1)(1) 3(1)(1), (F) over tilde 3(1)(1), and (F) over tilde 1(1)(1) 3(1)(1) bands are identified at 74 334(3), 74 121(5), 74 522(3), and 74 388(3) cm(-1), respectively, with much broader bandwidth (Gamma>100 cm(-1)) than the (D) over tilde-(X) over tilde and (F) over tilde-(X) over tilde origin bands, indicating that the dissociation is accelerated significantly in both of the (D) over tilde and (X) over tilde states when the antisymmetric C-H stretch (nu(3)) mode in the (D) over tilde and (F) over tilde states is excited.