Photoabsorption and fluorescence cross sections of SiCl4 in the region of 6.2–31 eV

Abstract

Absolute photoabsorption and fluorescence cross sections of gaseous SiCl 4 have been measured in the energy region 6.2-31 eV using synchrotron radiation as the light source. Higher order light from the 1-m Seya monochromator was suppressed by use of an Ar gas filter in the energy range 11.3-15.5 eV ͑110-80 nm͒ and a LiF window at h Ͻ 11.8 eV ͑105 nm͒. Emissions have been observed for the C 2 T 2 →à 2 T 2 and C 2 T 2 →X 2 T 1 processes of the SiCl 4 ϩ molecular ion and the à 1 B 1 →X 1 A 1 and 3 B 1 →X 1 A 1 of the SiCl 2 radical. The total fluorescence cross section has been determined to be 22.4Ϯ1.0 Mb at 21.22 eV. By comparing with the partial cross section for formation of the C 2 T 2 ionic state ͓Carlson et al., J. Chem. Phys. 84, 641 ͑1986͔͒, it has been concluded that the SiCl 4 ϩ (C 2 T 2 ) formed decays via radiative processes with quantum yield Ϸ1.The experimental results provide information on the breakdown pathways of the SiCl 4 ϩ (C 2 T 2 ) ion state. The bands observed in photoabsorption and fluorescence excitation spectra have been assigned as the ͑4s, np, and npЈ͒←3t 2 , ͑4s and np͒←1e, ͑4s and np͒←1e, ͑4s and 4 p͒←2t 2 , and ͑np and nd͒←2a 1 Rydberg series. The ionization energies for the (2t 2 ) Ϫ1 and (2a 1 ) Ϫ1 processes have been found to be 15.04Ϯ0.03 and 18.17Ϯ0.03 eV, respectively.

Vacuum–UV fluorescence spectroscopy of CCl4, SiCl4 and GeCl4 in the range 9–25eV

“…As shown by the groups of Ibuki and Tsuji, such experiments are common using fixed-energy metastable atom and discharge lamp sources, but are rare using dispersed radiation from a second-generation synchrotron source. We believe that our work complements but extends that of Ibuki et al on these three Group IV chlorides [8,18,20], who could only measure dispersed emission spectra at a small number of VUV energies. We are able to make such measurements at any VUV energy within the range of the monochromator used to disperse the synchrotron radiation, and therefore measure the thresholds directly for the different fluorescence decay channels.…”

“…The energies of excited states of Si* and Ge* atoms are well known [43], whereas emission in atomic carbon is not observed. Finally, we should note that non-resonant emission from the C2 T 2 third excited state of SiCl ϩ 4 and GeCl ϩ 4 has been observed, initially by us [14] but now by others [18,20], with thresholds at the AIE of this state of SiCl ϩ 4 and GeCl ϩ 4 of 15.0 and 14.6 eV, respectively.…”

“…Absolute absorption crosssections and photoionisation quantum yields have been measured in the range 50-100 nm by Kameta et al [17]. In a recent synchrotron study that is particularly pertinent to our work, Ibuki et al [18] have measured the absolute fluorescence cross-section of SiCl 4 down to 40 nm. In the energy range 10-14 eV, resonants peaks (as in process (1)) are observed in the fluorescence excitation spectrum which are assigned to transitions to Rydberg states of SiCl 4 which photodissociate to the ã3 B 1 and Ã1 B 1 states of SiCl 2 ; emission is then observed as the ã3 B 1 -X1 A 1 and Ã1 B 1 -X1 A 1 bands in SiCl 2 .…”

“…Very recently, Ibuki and Kamamoto [20] have observed absolute absorption and fluorescence cross-sections for GeCl 4 between 6 and 31 eV using synchrotron radiation. Assignments are given for transitions to Rydberg states of GeCl 4 below the first ionisation energy which photodissociate, in a similar manner to SiCl 4 [18], to the ã3 B 1 and Ã1 B 1 states of GeCl 2 .…”

Electronic properties, doping, and defects in chlorinated silicon nanocrystals

“…Moreover, the threshold energy of the absorption spectra of both molecules is a Rydberg transition (4s → 8t 2 ). 45,46 These excitonic effects leading to Rydberg states are not described by the ground state DFT. To our knowledge, Rydberg transitions have not been resolved for undoped silicon nanocrystals.…”