Elastic scattering of slow electrons by $n$-propanol and $n$-butanol

We report measured and calculated cross sections for elastic scattering of low-energy electrons by the alcohols $n$-propanol and $n$-butanol in the gas phase. The measurements were carried out using the relative-flow method with an aperture source rather than a conventional tube or capillary-array source, eliminating the need to know molecular diameters. The calculations employed two different implementations of the Schwinger multichannel variational method and included polarization effects. The differential cross sections are dominated by strong forward scattering due to the molecules’ large electric dipole moments, but near $10\mathrm{eV}$, they display structure at intermediate angles that is probably associated with shape resonances, notably a pronounced $f$-wave scattering pattern. Overall agreement between the measured and calculated results is fair. We compare the cross sections of these larger alcohols to those of methanol and ethanol, as well as to those of alkanes.

Figure 1

(Color online) Differential cross sections for elastic scattering of electrons by $n$-propanol. The measured values are indicated by red circles, the all-electron calculated values by thin blue lines, and the pseudopotential values by thick green lines.

Figure 2

(Color online) As in Fig. 1, for $n$-butanol.

Figure 3

(Color online) Calculated (pseudopotential) differential cross sections for elastic electron scattering by methanol, ethanol, $n$-propanol, and $n$-butanol at $10\mathrm{eV}$ impact energy. Methanol and ethanol results are from Ref. 6.

Figure 4

(Color online) Calculated (all-electron) differential cross sections for elastic electron scattering by $n$-propanol (left) and $n$-butanol (right), showing the evolution of the angular structure from $6\text{to}10\mathrm{eV}$ collision energy.

Figure 5

(Color online) Integral elastic cross sections for electron collisions with $n$-propanol and $n$-butanol. Red circles are experimental values, thin blue lines with squares results from all-electron calculations, and thick green lines with diamonds results from pseudopotential calculations. Open symbols and solid lines are propanol data; solid symbols and dashed lines are butanol data. See text for discussion.

Figure 6

(Color online) Momentum-transfer cross sections for electron collisions with $n$-propanol and $n$-butanol. Red circles are experimental values, thin blue lines with squares results from all-electron calculations, and thick green lines with diamonds results from pseudopotential calculations. Open symbols and solid lines are propanol data; solid symbols and dashed lines are butanol data.