Nonresonant two - photon mass analyzed threshold ionization and zero kinetic energy photoelectron investigation of the X̃ 2 B 1 ground state of CH 2 CO ¿ and CD 2 CO ¿
نویسندگان
چکیده
Rotationally resolved nonresonant two-photon mass analyzed threshold ionization ~MATI! and zero kinetic energy ~ZEKE! photoelectron spectra of CH2CO 1 and CD2CO 1 are reported. The spectra are dominated by the origin band and totally symmetric a1 vibrations, n4 ~C5C symmetric stretch! and n2 ~C5O asymmetric stretch! for CH2CO , and n1 ~C5O asymmetric stretch!, n3 ~C5C symmetric stretch!, and n4 (CD2 scissor! for CD2CO . In addition, several weaker bands are observed in the MATI spectra: n3 (CH2 scissor! in CH2CO ; b1 vibrations n5 and n6 ~C5C5O linear bend and CH2 wag! in both isotopomers; b2 vibration n8 (CD2 rock! for CD2CO ; b2 vibration n9 ~C5C5O linear bend! for CH2CO ; as well as overtones and combination bands. Rotational structure of the origin band is dominated by three very strong DKa561 bands with 2 orders of magnitude weaker DKa513 bands. A similar DKa561 three-band pattern is observed for the a1 vibrational modes. For the b1 modes a single-band pattern resulting from the DKa50 selection rule is present. Fundamental wave numbers for six vibrational modes of CH2CO 1 and seven modes of CD2CO 1 are determined. Rotational analysis of the partially resolved ZEKE spectra yields the ionization potentials (77539.462.0 cm for CH2CO and 77534.362.0 cm 21 for CD2CO) and rotational constants for the ground states of both ketene cations. © 2002 American Institute of Physics. @DOI: 10.1063/1.1506157#
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