Far-infrared optical constants of liquid acetonitrile at 238 to 343 K as measured with a synchrotron radiation source

Dielectric response and collective dynamics of acetonitrile

“…The above parameters of the Di + DHO + G fit yield a value of 35.84 for the static relative permittivity which is identical to the result of the D fit to the 0.1-89 GHz data and in excellent agreement with the highprecision capacitance measurement of ε (Table 1). Additionally, ε ∞ is in excellent agreement with the squared refractive index, n ∞ 2 = 1.81, reported by Ohba and Ikawa [15] as the high-frequency limit of the rotational contribution. This suggests that the present broadband data and its description by Eq.…”

“…1. At 25°C the thus obtainedε ν ð Þ were complemented at Freiburg by measurements in the 0.1-3 THz region using a THz-TDS instrument operating in reflection geometry at (298.2 ± 0.5) K [28] and combined with far-infrared data from the literature [15,20,22]. The obtained dielectric spectrum covering 0.1-8 THz is shown in Fig.…”

“…, for the D model, Eq. (2), applied to AN spectra in the frequency range 0.1 ≤ ν/GHz ≤ 89 as a function of temperature, T. Also included are the corresponding static permittivity, ε D = ε ∞,D + S D , and reference data, ε [29], for this quantity, as well as the squared refractive index, n ∞ 2 [15], associated with intramolecular polarizability. (2) (•) and from critically evaluated [29] capacitance measurements (line).…”

“…Molecular reorientation in AN was probed with NMR spectroscopy [9,10] and infrared/ Raman band shape analysis [11,12], revealing that the motions can be classified as anisotropic rotational diffusion. Far-infrared [13][14][15][16] and time-resolved optical Kerr effect (OKE) spectroscopy [17] of the collective dynamics in the sub-picosecond region showed that dipole libration predominates but significant contributions from induced moments and especially cross-correlations of permanent and induced dipoles are also present [5]. Dielectric spectroscopy in the microwave region indicated the influence of static and dynamic correlations on the relaxation time of the collective dipole moment [18].…”

“…So far, only a few investigations with data of limited accuracy for a small number of spot frequencies have explored this gap in the complex permittivity spectrum,ε ν ð Þ ¼ ε 0 ν ð Þ−iε 00 ν ð Þ [19][20][21], so that the transition of the motional regime of AN from short-time librations to rotational diffusion at long times is still not well known. It is the intention of this contribution to bridge the gap at 25°C by combining dielectric data collected in Regensburg in the frequency range of 0.1-89 GHz with measurements at Freiburg covering 0.1-3 THz and selected far-infrared spectra (1-8 THz, 30-240 cm −1 ) from the literature [15,20,22]. Surprisingly, also no good quality data for the temperature dependence ofε v ð Þ in the microwave region is available.…”