The rotational spectrum, nuclear field shift effects, 195Pt nuclear spin–rotation constant, and electric dipole moment of PtSi

The pure rotational spectrum of the <f>X1Σ+</f> ground electronic state of platinum monosilicide has been measured for nine isotopomers. For the most abundant isotopomer, 194Pt28Si, the <f>J=1–0</f> and the <f>J=2–1</f> transitions were recorded up to the fourth vibrationally excited state. The data set obtained enabled a multi-isotopomer fit to a Dunham-type expression and the constants <f>Y01</f>, <f>Y02</f>, <f>Y11</f>, <f>Y21</f>, and <f>Y31</f> were determined. In the process of fitting the data it was necessary to include Born–Oppenheimer breakdown correction terms and the values and significance of these terms are discussed. Strong evidence is presented indicating within the rotational spectrum the presence of field shift effects due to the finite size of the Pt nucleus. The nuclear spin–rotation constant, <f>CI</f>(195Pt) is found to be 30.98(157) kHz in the ground vibrational state. Hyperfine structure arising from the 29Si nucleus was not observed. The measurement of Stark shifts in the rotational spectrum of PtSi has enabled the determination of the dipole moments for the 194Pt28Si and 196Pt28Si isotopomers. [Copyright &y& Elsevier]