Observation of the d3Πg←c3Σu+ band system of C2

A new band system of C-2, d (3)Pi(g)<- c (3)Sigma(+)(u) is observed by laser induced fluorescence spectroscopy, constituting the first direct detection of the c (3)Sigma(+)(u) state of C-2. Observations were made by laser excitation of c (3)Sigma(+)(u)(v(')=0) C-2, produced in an acetylene discharge, to the d (3)Pi(g)(v(')=3) level, followed by detection of Swan band fluorescence. Rotational analysis of this band yielded rotational constants for the c (3)Sigma(+)(u)(v(')=0) state: B-0=1.9218(2) cm(-1), lambda(0)=-0.335(4) cm(-1) and gamma(0)=0.011(2) cm(-1). The vibrational band origin was determined to be nu(3-0)=15861.28 cm(-1). (c) 2006 American Institute of Physics.