Rotationally resolved REMPI spectra of CaH in a molecular beam

Rotationally resolved spectra of the Call radical using a supersonic molecular beam are reported. Thus, high energy resolution of the (I + l') REMPI spectra corresponding to the A <-- X and B <-- X electronic transitions were measured which allowed for the first time a clear and precise analysis of the low rotational part (J less than or equal to 7) of the CaH spectrum. A comparison with previous studies revealed that the commonly accepted energy separation between the two band heads of B - X (nu' = 1, nu' = 0) of 10 cm(-1) is not correct. A value of ca. 1.6 cm(-1) was found to be more realistic. On the other hand, the present study confirmed that the perturbation appears, only for nu' = 1, N' > 3 of the B state. (C) 2002 Elsevier Science (USA).