The spectroscopic characterization of the vibrational force field for the transient species of formyl cations
Abstract
The purpose of this investigation was to determine the spectroscopic constants associated with the force field for HCO+ and DCO + and to establish an excitation pathway which accessed high-lying, rovibrational states in the 1Σ+ electronic state of HCO+. Resonant two-photon ionization (R2PI) measurements from selected, rotational lines in the 3pπ 2Π Rydberg state yielded autoionization spectra with Rydberg series converging to 1Σ+ (0310) and (0330) for HCO+ and (0110), (0200) and (0220) for DCO+. Also, R2PI from the P(1) rotational line in the B 2A′ valence electronic state of HCO was used to measure the photoionization spectrum of highly excited, vibrational states of HCO+. Double-resonance photoionization efficiency spectroscopy produced ionization efficiency spectra for HCO and DCO from selected, rotational lines in the 3pπ 2Π (000) Rydberg state. All autoionization spectra were fitted with an unperturbed Rydberg formula resulting in energetic positions for the rovibrational ionization potentials of HCO+ and DCO+. Utilizing these ionization potentials, the harmonic frequency (ω2 = 842.57 cm−1), anharmonic constants (x22 = −2.53 cm−1 and g22 = 3.26 cm−1) and the B[030] = 1.50 cm−1 rotational constant for HCO+ were calculated. For DCO+, all its force field constants were calculated with the exception of ω1 and x11. The photoionization efficiency spectra for (000) DCO together with its (0110) autoionization spectrum yielded the first high-resolution adiabatic ionization potential for DCO (65616 cm −1) and the ν2 fundamental for DCO+ (666 cm−1). An excitation scheme which accessed highly excited, rovibrational states in HCO+ was validated with the measured photoionization spectrum from the B 2A′ electronic state. This scheme provides a gateway for future characterization of these states and the isomerization barrier where HCO+ converts to COH+. However, zero-kinetic energy pulsed field ionization spectroscopy must be used to resolve the existing discrete structure.
Degree
Ph.D.
Advisors
Grant, Purdue University.
Subject Area
Chemistry
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