Emission spectra of SiF3

Abstract

Emission spectra of SiF3 radical were observed from photodissociative excitation of SiF4 at 99.1, 95.5, and 92.3 nm. The spectra show a broad visible band in the 350–800 nm region, a UV band in 290–340 nm, and a weak band in 240–280 nm. The visible band resembles the chemiluminescence spectra observed from etching of silicon by F or XeF2.

A theoretical study of the electronic spectroscopy of the SiF3 radical

“…This Letter reports such calculations. We show that excited states of this radical do lie at energies consistent with the observations of Suto et al [5] and Biehl et al [8]. However, we calculate that the radiative lifetime of the upper state of an allowed electronic transition in any region of the visible spectrum, 400-800 nm, cannot be as low as 3.9 ns.…”

“…5.3 to 0.9 eV or 230-1360 nm (Table 1) ; the lowerenergy threshold is determined by the smallest gap between the à and X states which pertains at planarity ( Figure 1). The experiments of Suto et al [5] and Biehl et al [8] cannot detect the predicted high-wavelength region due to the insensitivity of photomultiplier tubes above ca. 800 nm.…”

“…Figure 1 shows Figure 1). Thus we might 5 expect to see an emission band extending from ca. 5.3 to 0.9 eV or 230-1360 nm (Table 1) ; the lowerenergy threshold is determined by the smallest gap between the à and X states which pertains at planarity ( Figure 1).…”

“…4 In all cases, the strongest reason for assigning the visible emission band to the SiF 3 radical is not spectroscopic, but thermochemical. Using the enthalpies of formation of SiF x determined from a guided ion beam study of Fisher et al [10] [5] are energetically allowed for excitation energies in the range 12.4 to 13.6 eV. Unlike CF 3 [11], however, there have been no ab initio calculations on the energies and radiative lifetimes of excited states of SiF 3 to confirm these assignments.…”

“…Second, Suto et al dispersed the emission induced from SiF 4 [5] and SiF 3 H [6] , both photoexcited with fixed-wavelength vacuum-UV line sources between 90 and 100 nm. Two broad and unstructured bands, spanning the ranges 290-340 and 400-800 nm, were observed.…”