High resolution infrared spectra of the linear carbon cluster C_7:The v'4 stretching fundamental band and associated hot bands

摘要

High resolution infrared spectra of the v_4 fundamental antisymmetric stretching mode and associated hot bands of the linear carbon cluster C_7 were recorded using a tunable diode laser spectrometer in the frequency range of 2135-2141 cm~(-1).Spectra of the v_4 fundamental,v_4+v_(11)-v_(11),v_4+2v_(11)-2v_(11),and v_4+v_8-v_8,bands have been analyzed and are compared to recent experimental results and high level ab initio calculations.In particular,the presented results give experimental evidence for the rigidity of C_7 and confirm theoretical predictions of a rather regular chain molecule,similar to the cases of C_4,C_5,and C_9.For the two energetically low-lying bending modes,v_8 and v_(11),the rotational constants differ by less than 0.2%,from the ground state value,B_0=0.030 624 4(28) cm~(-1),in good agreement with the recent calculations by Botschwina [Chem.Phys.Lett.354,148 (2002)].From the hot band analysis and the l-type doubling constant q,experimental values for the band origins of the v_8 and v_(11) fundamentals have been derived.