| Abstract: | A powerful argon ion laser was used to excite gaseous chlorine molecules resonantly from the X1Σ ground electronic state to the  excited electronic state. Three progressions of P, R doublets which correspond to the excitation from J=37, 13 and 39 of v=0 of the X1Σ state to v′=22, J′=38; v′=18, J′=12 and v′=16, J′=38 of the  state, respectively, and then decaying to various vibrational levels of the X1Σ state were observed. Of those, only the excitation from v=0, J=38 to v′=22, J′=38 transition has been reported before. Due to the extremely small transition probabilities, the spectral lines are much weaker than those of iodine and bromine. Their positions and their relative intensities were analyzed and compared with the result calculated from the known molecular constants and with the known Franck-Condon factors. Our data are consistent with the calculated results within the range of experimental error. |
