Mateusz Zawadzki

Spatial interference from well-separated split condensates

We use magnetic levitation and a variable-separation dual optical plug to obtain clear spatial interference between two condensates axially separated by up to 0.25 mm-the largest separation observed with this kind of interferometer. Clear planar fringes are observed using standard (i.e., nontomographic) resonant absorption imaging. The effect of a weak inverted parabola potential on fringe separation is observed and agrees well with theory.

Scattering of electrons from 1-butene, H2C=CHCH2CH3, and 2-methylpropene, H2C=C(CH3)2, molecules

We report absolute grand total cross sections (TCSs) for electron scattering from 1-butene (H2C=CHCH2CH3) and 2-methylpropene (H2C=C(CH3)2) molecules, measured at electron impact energies ranging from 1 to 400 eV and from 1 to 350 eV, respectively, using a linear electron-transmission technique. The general shape of cross sections for both butene isomers looks similar. Two structures in each TCS energy curve are discernible: a small peak in the vicinity of 2.3 eV and a pronounced very broad enhancement with the maximum located around 8 eV. The magnitude of TCS for 2-methylpropene appears somewhat higher than that for 1-butene below 20 eV, while above 70 eV the TCS curves practically overlap. In addition, comparison is made of TCSs for an ethylene (H2C=CH2) molecule and its mono and double methyl-substituted derivatives: propene (H2C=CHCH3) and 2-methylpropene. (Some figures may appear in colour only in the online journal)

Electron-scattering cross sections for 1-pentene, H2C=CH–(CH2)2CH3, molecules

Cross sections, both experimental and theoretical, are reported for electron scattering from 1-pentene (C5H10) molecules. Absolute grand-total cross sections (TCSs) were measured at electron impact energies ranging from 1 to 300 eV, using a linear electron-transmission technique. The dominant behaviour of the experimental TCS energy function is a distinct asymmetric enhancement with the maximum located around 6.5 eV. Discernible are also three weak TCS structures: a small peak in the vicinity of 1.8 eV and two broad shoulders located between 10 and 30 eV. The additivity rule was employed to calculate the elastic cross section (ECS) from 20 to 3000 eV, while the binary-encounter-Bethe approach was used for the computation of the ionization cross section (ICS), from the threshold up to 3000 eV. Within 30 and 300 eV, the sum of computed cross sections (ECS+ICS) quite reasonably reproduces the experimental TCS values. Comparison is also made between the experimental TCS energy curve for 1-pentene (H2C=CH–(CH2)2CH3) and those measured for the ethylene (H2C=CH2) molecule and its substituted derivatives: propene (H2C=CH–CH3) and 1-butene (H2C=CH–CH2CH3). (Some figures may appear in colour only in the online journal)

Scattering of electrons by a 1,2-butadiene (C4H6) molecule: measurements and calculations

We present the results of experimental and theoretical study on electron collisions with a 1,2-butadiene (H2C=C=CHCH3) molecule. Absolute grand-total cross sections (TCSs) were measured using a linear electron-transmission method for collision energies in the 0.5–300 eV range. Two distinct features in the TCS energy curve were detected: a narrow peak located at 2.3 eV and a broad enhancement centered around 9 eV. We attributed these features to the formation of negative-ion resonant states, based on comparisons with the existing data for other targets of similar structure. Experimental findings indicate a bonding effect on the TCS when confronting TCS curves for allenes with those for respective acetylenes. Clear differences in experimental TCS energy dependences for C4H6 isomers (1,2-butadiene, 1,3-butadiene, 1-butyne and 2-butyne) show on the isomeric effect. The independent atom approximation was employed to calculate the elastic (ECS) cross section from 25 to 3000 eV, while the binary-encounter-Bethe approach was used for computation of the ionization (ICS) cross section, from the threshold up to 3 keV. The sum of computed cross sections (ECS+ICS) quite reasonably reproduces the experimental TCS values above 35 eV. The reported TCS experimental values are not corrected for the forward-angle scattering effect.

Total cross section for low-energy electron scattering from formic acid, (HCOOH), molecules

Total cross section (TCS) for low-energy electron scattering from formic acid molecules has been measured using electrostatic electron spectrometer working in linear transmission mode. Two local maxima centered around 1.7 eV and 7.8 eV have been observed and associated with resonant scattering processes.

Dissociation of 2-oxopropanoic acid by low energy electrons

Mateusz Zawadzki∗†1, Jaroslav Koc̆is̆ek∗, Juraj Fedor∗ ∗ J. Heyrovský Institute of Physical Chemistry vvi, Academy of Sciences of the Czech Republic, Dolejs̆kova 3, 182 23 Praha, Czech Republic † Atomic Physics Division, Department of Atomic, Molecular and Optical Physics, Faculty of Applied Physics and Mathematics, Gdańsk University of Technology, ul. Gabriela Narutowicza 11/12, 80-233 Gdańsk, Poland

Electron collisions with methyl-substituted ethylenes: Cross section measurements and calculations for 2-methyl-2-butene and 2,3-dimethyl-2-butene

We report electron-scattering cross sections determined for 2-methyl-2-butene [(H3C)HC = C(CH3)2] and 2,3-dimethyl-2-butene [(H3C)2C = C(CH3)2] molecules. Absolute grand-total cross sections (TCSs) were measured for incident electron energies in the 0.5-300 eV range, using a linear electron-transmission technique. The experimental TCS energy dependences for the both targets appear to be very similar with respect to the shape. In each TCS curve, three features are discernible: the resonant-like structure located around 2.6-2.7 eV, the broad distinct enhancement peaking near 8.5 eV, and a weak hump in the vicinity of 24 eV. Theoretical integral elastic (ECS) and ionization (ICS) cross sections were computed up to 3 keV by means of the additivity rule (AR) approximation and the binary-encounter-Bethe method, respectively. Their sums, (ECS+ICS), are in a reasonable agreement with the respective measured TCSs. To examine the effect of methylation of hydrogen sides in the ethylene [H2C = CH2] molecule on the TCS, we compared the TCS energy curves for the sequence of methylated ethylenes: propene [H2C = CH(CH3)], 2-methylpropene [H2C = C(CH3)2], 2-methyl-2-butene [(H3C)HC = C(CH3)2], and 2,3-dimethyl-2-butene [(H3C)2C = C(CH3)2], measured in the same laboratory. Moreover, the isomeric effect is also discussed for the C5H10 and C6H12 compounds.