Photoabsorption, photoionization, and Auger processes at the carbonKedge inCH3I

Abstract

The dynamics of photoabsorption, photoionization, and the associated Auger decay have been investigated at the carbon K-edge in methyl iodide (CH3I) using linearly polarized synchrotron radiation. Ion yield measurements were used to investigate transitions in the pre-edge region due to excitations into either unoccupied valence or Rydberg states. The assignment of these transitions was achieved through comparison with theoretical X-ray absorption spectra calculated using time-dependent density functional theory, within the Tamm-Dancoff approximation.Several of the Rydberg states belonging to series converging onto the C 1s ionization limit exhibit significant vibrational structure that is also interpreted using theoretical calculations. The C 1s in CH3I photoelectron spectrum was measured, and the observed vibrational structure was assigned with the aid of theoretical predictions. Polarization dependent, resonantly excited, valence shell photoelectron spectra were recorded at photon energies coinciding with the C 1s → *, C 1s → 6sa1 and C 1s → 6pe transitions in CH3I, thereby allowing photoelectron angular distributions to be determined. The non-resonantly excited C(KVV) Auger electron spectrum was measured and some of the features observed at high kinetic energies were attributed to transitions into valence orbitals possessing significant iodine character. The contributions of participator and spectator Auger decay to the resonantly excited photoelectron spectra have been assessed. The influence of participator decay appears minor whereas spectator decay results in the enhanced population of satellite states.

Modeling of the spectroscopy of core electrons with density functional theory

“…Alternative approaches include a projection method that allows transitions within a specified energy range to be determined, 105 and the resonant converged complex polarization propagator approach of Norman and co‐workers 106,107 . The application of TDDFT to study X‐ray absorption spectroscopy is very diverse considering both K‐edge and L‐edge spectra, and illustrative examples include biological systems, 108‐110 metal complexes, 111 radicals, 112 molecules on surfaces, 113,114 ionic liquids, 115 liquid water, 63,64 lanthanide complexes, 116,117 and vibrationally resolved spectra 118 …”

Medium-assisted van der Waals dispersion interactions involving chiral molecules

“…(20) runs over discrete variables of molecular states m, l, electric or magnetic nature of the noise source λ, spatial components i, as well as continuous variables of frequency and position. Making use of the integral relation (19) leads to the contribution coming from case (1)a to the fourth-order energy shift as…”

“…Substitution of these into Eq. (20) and making use of the integral relation (19) leads for the contribution of diagram (1)a in Fig. 3, again, to Eq.…”

“…After substituting these matrix elements in Eq. (51), the implicitly included summations over λ j (j = e, m) and position integrals can be performed on making use of the integral relation (19) to lead to the contribution from diagram (1)a in Fig. 6 as…”

“…Other manifestations of molecular handedness include differential absorption (circular dichroism) [6] and differential scattering (Rayleigh and Raman) [7] of circularly polarized light, their nonlinear analogues [8], as well as other chiroptical spectroscopies that depend quadratically or on higher powers of the strengths of electromagnetic fields, such as sum-frequency and second-harmonic generation [9][10][11]. Many of these phenomena have also been predicted to occur when the incident radiation is of the structured type [12][13][14][15][16][17][18][19]. Because chiral compounds possess reduced or no elements of symmetry, selection rules normally in operation that are used to determine whether spectroscopic transitions are allowed or forbidden are considerably relaxed, or no longer apply.…”