New Fourier transform infrared emission spectra of CaH and SrH: combined isotopomer analyses with CaD and SrD

In a search for the infrared spectra of gaseous CaH2 and SrH2, we obtained new Fourier transform infrared emission spectra of CaH and SrH, but no evidence of the metal dihydrides. The vibration-rotation bands from v ¼ 1!0 to v ¼ 4!3 of 40CaH and 88SrH, and the v ¼ 1!0 band of 87SrH and 86SrH were observed in the X2Sþ ground electronic states. The new data were combined with the previous ground state data, obtained from diode laser infrared and pure rotational spectra, and the spectroscopic constants for v ¼ 0 to 4 of 40CaH and 88SrH were determined. In addition, the Dunham constants and the Born–Oppenheimer breakdown correction parameters were obtained using the previous ground state data for CaD and SrD in combined isotopomer fits. The equilibrium vibrational constants ðveÞ for CaH and SrH were found to be 1298.400(1) and 1207.035(1) cm21, respectively, while the equilibrium rotational constants ðBeÞ are 4.277043(4) and 3.673495(4) cm21. The equilibrium bond distances ðreÞ were determined to be 2.0023603(9) A ° for CaH and 2.1460574(10) A ° for SrH. q 2004 Elsevier B.V. All rights reserved.