PNNL

Abstract

The research described in this product was performed in part in the Environmental Molecular Sciences Laboratory, a national scientific user facility sponsored by the Department of Energy's Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory. The vacuum ultraviolet (VUV) laser pulsed field ionization-photoelectron (PFI-PE) spectrum of trans-1,3-butadiene (trans-CH2==CHCH==CH2) has been measured in the region of 0–1700 cm-1 above its ionization energy (IE) to probe the vibrational modes vi + (i=1–18) of trans-CH2==CHCH==CH2 +. The high-frequency vibrational modes vi + (i=19, 22, and 23) of trans-CH2==CHCH==CH2 + have also been probed by the VUV-infrared-photoinduced Rydberg ionization (VUV-IR-PIRI) measurement. On the basis of the semiempirical simulation of the origin VUV-PFI-PE band, the IE(trans-CH2==CHCH==CH2) is determined to be 73 150.1±1.5 cm-1 (9.06946±0.00019 eV). This value has been used to benchmark the state-of-the-art theoretical IE prediction based on the CCSD(T,Full)/CBS procedures, the calculation of which is reported in the present study. The vibrational bands observed in the VUV-PFI-PE and VUV-IR-PIRI spectra were assigned based on ab initio anharmonic vibrational frequencies and Franck–Condon factor calculations for the photoionization transitions. Combining the VUV-PFI-PE and VUV-IR-PIRI measurements, 17 fundamental vibrational frequencies of trans-CH2==CHCH==CH2 + have been determined, including v1 +=182±3, v2 +=300±3, v3 +=428±3, v4 +=514±3, v5 +=554±5, v6 + =901±3, v7 +=928±5, v8 +=994±3, v9 +=1008±5, v10 + =1094±5, v13 + =1258±3, v14 + =1293±3, v16 + =1479±3, v18 + =1620±3, v19 + =2985±10, v22 + =3030±10, and v23 + =3105±10 cm-1.