Rotationally resolved electronic absorption spectra of triacetylene cationin a supersonic jet

The rotationally resolved cold spectra (T-rot approximate to 17 K) of the A (2)Pi(g) <-- X(2)Pi(g) 0(0)(0) and 4(0)(1) transitions of triacetylene cati on have been recorded in a supersonic jet. A discharge modulation in combin ation with the external frequency modulation of a cw ring laser is used to enhance detection sensitivity. The advantage of obtaining the spectra of su ch species under jet conditions is shown by comparison with measurements in a cell of the 4(0)(1) vibronic transition. The combined analyses of the ro tational structure yields rotational and spin-orbit constants for the nu(4) = 1 level of the A(2)Pi(g) state. (C) 1999 Elsevier Science B.V. All right s reserved.