Vibrational Spectra and Structures of Neutral Si_mC_n Clusters (m + n = 6): Sequential Doping of Silicon Clusters with Carbon Atoms

Abstract

Vibrational spectra of mixed silicon carbide clusters Si(m)C(n) with m + n = 6 in the gas phase are obtained by resonant infrared-vacuum-ultraviolet two-color ionization (IR-UV2CI for n ≤ 2) and density functional theory (DFT) calculations. Si(m)C(n) clusters are produced in a laser vaporization source, in which the silicon plasma reacts with methane. Subsequently, they are irradiated with tunable IR light from an IR free electron laser before they are ionized with UV photons from an F(2) laser. Resonant absorption of one or more IR photons leads to an enhanced ionization efficiency for Si(m)C(n) and provides the size-specific IR spectra. IR spectra measured for Si(6), Si(5)C, and Si(4)C(2) are assigned to their most stable isomers by comparison with calculated linear absorption spectra. The preferred Si(m)C(n) structures with m + n = 6 illustrate the systematic transition from chain-like geometries for bare C(6) to three-dimensional structures for bare Si(6). In contrast to bulk SiC, carbon atom segregation is observed already for the smallest n (n = 2).

Characterization of neutral boron-silicon clusters using infrared spectroscopy: The case of Si6B

“…Larger SinBm clusters (n+m20) can also be generated. However, the isotope distribution of 28,29,30 Si complicates the assignment of the mass spectra. Note that a 11 B-enriched boron target is used here to simplify the isotope pattern.…”

“…Surprisingly, no spectroscopic data are available for B-doped silicon clusters in any charge state. Here, we combine infraredultraviolet two-color ionization (IR-UV2CI) spectroscopy [27] with quantum chemical simulations to determine the structure of Si6B, a strategy recently applied to a variety of (doped) silicon clusters [25,[27][28][29][30].…”

Vibrational spectra and structures of neutral Si6X clusters (X = Be, B, C, N, O)

“…50 We note that these methods have proven reliable for silicon-containing clusters reported previously. 14,38 At such levels, detailed information about the linear IR absorption spectra, ionization energies, and natural bond orbital populations is obtained.…”

“…12,[18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34], only a few experiments have been reported in the gas phase. 8,14,[35][36][37][38] By sequential doping of silicon clusters with carbon atoms, i.e., for Si m C n with m + n = 6, we recently observed a systematic transition from one-dimensional geometries for pure C 6 to three-dimensional structures for pure Si 6 . 38 In this study, we present complementary experimental and theoretical results on silicon clusters doped with first row elements (Si 6 X, with X = Be, B, C, N, O).…”

“…8,14,[35][36][37][38] By sequential doping of silicon clusters with carbon atoms, i.e., for Si m C n with m + n = 6, we recently observed a systematic transition from one-dimensional geometries for pure C 6 to three-dimensional structures for pure Si 6 . 38 In this study, we present complementary experimental and theoretical results on silicon clusters doped with first row elements (Si 6 X, with X = Be, B, C, N, O). Structures of these clusters have been predicted using DFT-based basin hopping (BH) global optimization.…”