Interpretation of the vacuum ultraviolet photoabsorption spectrum of iodobenzene by ab initio computations

Abstract

Identification of many Rydberg states in iodobenzene, especially from the first and fourth ionization energies (IE1 and IE4, X(2)B1 and C(2)B1), has become possible using a new ultraviolet (UV) and vacuum-ultraviolet (VUV) absorption spectrum, in the region 29 000-87 000 cm(-1) (3.60-10.79 eV), measured at room temperature with synchrotron radiation. A few Rydberg states based on IE2 (A(2)A2) were found, but those based on IE3 (B(2)B2) are undetectable. The almost complete absence of observable Rydberg states relating to IE2 and IE3 (A(2)A2 and B(2)B2, respectively) is attributed to them being coupled to the near-continuum, high-energy region of Rydberg series converging on IE1. Theoretical studies of the UV and VUV spectra used both time-dependent density functional (TDDFT) and multi-reference multi-root doubles and singles-configuration interaction methods. The theoretical adiabatic excitation energies, and their corresponding vibrational profiles, gave a satisfactory interpretation of the experimental results. The calculations indicate that the UV onset contains both 1(1)B1 and 1(1)B2 states with very low oscillator strength, while the 2(1)B1 state was found to lie under the lowest ππ(∗) 1(1)A1 state. All three of these (1)B1 and (1)B2 states are excitations into low-lying σ(∗) orbitals. The strongest VUV band near 7 eV contains two very strong ππ(∗) valence states, together with other weak contributors. The lowest Rydberg 4b16s state (3(1)B1) is very evident as a sharp multiplet near 6 eV; its position and vibrational structure are well reproduced by the TDDFT results.

Organic Aerosols in Anoxic and Oxic Atmospheres of Earth-like Exoplanets: VUV-MIR Spectroscopy of CHON Tholins

“…VUV transmission spectra were measured on the AU-UV beam line at the ASTRID2 5 synchrotron at Aarhus University, Denmark (Palmer et al 2015). Thin films deposited on MgF 2 windows were placed in the lollipop sample holder, able to mount up to four samples.…”

Electronic excitation of furfural as probed by high-resolution vacuum ultraviolet spectroscopy, electron energy loss spectroscopy, and ab initio calculations

“…The apparatus used for the measurement of photoabsorption spectra has also undergone several alterations, since that which was originally described in Eden et al 33 These changes have recently been described in Ref. 34, to where the reader is referred for more detail. Briefly, the gas cell has a path length of 15.5 cm and is fitted with a heated 1 Torr baratron capacitance manometer (Setra model 774).…”

Electron‐Induced Reactions in 3‐Bromopyruvic Acid

“…The experimental setup was reported in detail by Palmer et al [26] In brief, ag as cell with ap ath length of 15.5 cm was mounted on the output of the monochromator,w ith aM gF 2 window separating it from the UHV of the beam line. The experimental setup was reported in detail by Palmer et al [26] In brief, ag as cell with ap ath length of 15.5 cm was mounted on the output of the monochromator,w ith aM gF 2 window separating it from the UHV of the beam line.…”