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Absolute cross sections for electron impact dissociative excitation and ionization of CD+ leading to the formation of ionic products ( D+, C+, C2+ and C3+) are reported in the energy range from their respective thresholds to 2.5 keV. Around the maximum, cross sections are found to be ( 10.5 +/- 1.0) x 10(-17) cm(2), ( 20.6 +/- 3.5) x 10(-17) cm(2), ( 1.20 +/- 0.11) x 10(-17) cm(2) and ( 8.2 +/- 1.5) x 10(-20) cm(2) for D+, C+, C2+ and C3+, respectively. In the very low- energy region, dissociative excitation leading to the C+ formation dominates over the D+ one. The cross section for dissociative ionization ( C+ + D+ formation) is found to be ( 6.9 +/- 1.3) x 10(-17) cm(2) around 105 eV and the corresponding threshold energy is ( 22.1 +/- 0.5) eV. The animated crossedbeams method is used and the analysis of ionic product velocity distributions allows the determination of the kinetic energy release distributions. They are seen to extend from 0 to 15 eV both for C+ and for D+, and up to 40 eV both for C2+ and for C3+. For singly charged products, the comparison of the present energy thresholds and kinetic energy release with published data allows the identification of states contributing to the observed processes. In particular, contributions from primary ions formed in the a(3)Pi metastable state are perceptible. At fixed electron energy, the cross sections for the various ionization channels are seen to reduce exponentially with the potential energy of each dissociated ion pair. Anisotropies are estimated to be in the range 8 +/- 2% for both C+ and D+. The total CD+ single ionization cross section calculated by application of the Deutsch - Mark formalism is found to be in good agreement with experimental results.

Absolute cross sections for electron impact ionization of CO+ leading to the formation of doubly and triply charged products (CO2+, C2+ and O2+, C3+ and O3+) are reported in the energy range from their respective thresholds to 2500 eV. Around the maximum, cross section values are found to be ( 13.36 +/- 0.56) x 10(-18) cm(2), ( 5.58 +/- 0.55) x 10(-18) cm(2) and (1.37 +/- 0.14) x 10(-18) cm(2) for CO2+, C2+ and O2+, respectively, and (28.3 +/- 7.0) x 10(-21) cm(2) and (2.4 +/- 0.7) x 10(-21) cm(2) for C3+ and O3+, respectively. The analysis of ionic product velocity distributions, obtained by means of a crossed electron-ion beam set-up, allows the determination of the kinetic energy release distributions. They are seen to extend from 0 to 50 eV both for C2+ and O2+. The mean kinetic energy releases for C3+ and O3+ are found to be 33 +/- 5 eV and 39 +/- 9 eV, respectively. The cross sections are seen to depend exponentially on the potential energy of each dissociated ion pair. The total single CO+ ionization cross section calculated by application of the Deutsch-Mark ( DM) formalism is found to be in good agreement with the experimental results.

Recent experiments (Nagesha and MacAdam 2003 Phys. Rev. Lett. 91 113202) determined electron-impact ionization cross sections for 11 selected Na(ns) and Na(nd) Rydberg states (with the principal quantum number n in the range of 35–51), which exceeded predictions based on the well-known Vriens–Smeets (VS) fitting formula by more than an order of magnitude. This motivated us to extend the semi-classical Deutsch–Mark (DM) formalism to the calculation of ionization cross sections of these Na Rydberg states. The results show that the calculated DM ionization cross sections also lie below the experimentally determined cross sections by factors ranging from 15 to about 40. This indicates either that the ionization of these Rydberg atoms involves some new aspects or mechanisms that are not adequately described by models based on low-n data, or that the very difficult experiments suffered from a systematic error in the absolute calibration process that remained unrecognized.

We report absolute partial cross sections for the formation of selected positive and negative ions resulting from electron interactions with uracil. Absolute calibration of the measured partial cross sections for the formation of the three most intense positive ions, the parent C4H4N2O+2 ion and the C3H3NO+ and OCN+ fragment ions, was achieved by normalization of the total single uracil ionization cross section (obtained as the sum of all measured partial single ionization cross sections) to a calculated cross section based on the semi-classical Deutsch–Mark formalism at 100 eV. Subsequently, we used the OCN+ cross section in conjunction with the known sensitivity ratio for positive and negative ion detection in our apparatus (obtained from the well-known cross sections for SF+4 and SF−4 formation from SF6) to determine the dissociative attachment cross section for OCN− formation from uracil. This cross section was found to be roughly an order of magnitude smaller, about 5 × 10−22 m2 at 6.5 eV, compared to our previously reported preliminary value. We attribute this discrepancy to the difficult determination of the uracil target density in the earlier work. Using a reliably calculated cross section for normalization purposes avoids this complication.

We report the first application of the semi-classical Deutsch-Mark formalism to the calculation of the absolute electron-impact ionization cross section of simple molecular ions. Our calculated cross sections for the electron-impact ionization of CO2+ and N-2(+) are compared with recently published (as well as with unpublished) experimental data for these molecular ions. The level of agreement between the experimentally determined and the calculated cross section is satisfactory, in particular in view of the added complications in the experimental determination of ionization cross sections of molecular ions.

We used the Deutsch-Mark (DM) formalism to calculate atomic K-shell ionization cross sections for the elements chromium (Cr), nickel (Ni), copper (Cu), scandium (Sc) and vanadium (V). The calculated K-shell ionization cross sections were compared with recently measured K-shell ionization cross sections and good to satisfactory agreement has been found for all five elements. Moreover, when compared with other available calculated K-shell ionization cross sections for these five atoms using a variety of theoretical methods and semi-empirical formulae, the predictions of the DM formalism achieve a level of agreement with experimental data that is as good as, or sometimes better than, the predictions from the other methods.

We measured absolute cross sections for the electron-impact ionization and dissociative ionization of the C2F5 free radical from threshold to 200 eV using the fast-neutral-beam technique. The electron-impact ionization of C2F5 is dominated by two channels, the formation of the CF3+ fragment ion which has the largest partial ionization cross section with a value of 3.5 × 10-16 cm2 at 70 eV and the formation of the C2F5+ parent ion with a cross section of 1.3 × 10-16 cm2 at 70 eV. Both partial cross sections have error margins of about ±15%. All other partial ionization cross sections have maximum cross section values of less than 0.1 × 10-16 cm2. The total single C2F5 ionization cross sections at 70 eV (derived from the two measured partial ionization cross sections and an estimate for the sum of the cross sections for all weaker, unobserved ionization processes) was found to be about 5 × 10-16 cm2. A comparison of the measured total single-ionization cross sections with a calculated cross section, using a modified additivity rule, shows good agreement up to an electron energy of 50 eV, but poor agreement at higher impact energies. This behaviour is somewhat similar to that observed for the CFx (x = 1-3) free radicals, but it is very different from the excellent agreement between the calculated and measured total single-ionization cross sections that was observed for the stable molecules CF4 and C2F6.

The semiclassical Deutsch-Mark (DM) formalism was used to calculate absolute cross sections for the electron-impact ionization of metastable atoms such as metastable rare-gas atoms and metastable mercury and cadmium atoms from threshold to 200 eV. Systematic trends in the calculated cross section data are discussed and a comparison is made with available experimental data and with other calculations. Specifically, we calculated separately the contributions to the ionization cross sections arising from the removal of the single excited electron in the outermost subshell and the removal of the lower-lying inner-shell electrons.

We employed the fast-neutral-beam technique in a measurement of the absolute partial cross section for the formation of ions following controlled electron-impact ionization of the fullerene from threshold to 200 eV. Our measurement is the first report of an absolute measurement of this cross section which does not employ any normalization procedure and which does not rely on the use of controversial vapour pressure versus temperature data for to determine the number density in the ion source. All quantities that determine the ionization cross section were measured directly in our apparatus. We found a peak value for the parent ionization cross section of in the energy range between 70 and 80 eV. This value is in very good agreement (to within 5%) with the cross section reported earlier by Matt et al (1996 J. Chem. Phys. 105 1880) who employed a novel normalization procedure. Our cross section is significantly lower than the cross sections reported by several other investigators who relied on vapour pressure data in their absolute calibration.

The semiclassical Deutsch - Mark (DM) formalism for the calculation of absolute cross sections for the single ionization of atoms has been extended to the calculation of cross sections for the multiple ionization of ground state atoms (degree of ionization m > 3). Comparisons are presented with the predictions of two recently published semi-empirical methods and with available experimental data for some selected targets. The DM formalism is conceptually straightforward to apply; the semi-empirically determined parameters can easily be related to physical quantities and the formalism has already been successfully applied to the single ionization of atoms, ions, molecules, radicals and clusters, as well as to the double and triple ionization of atoms. In those cases where predictions from all three methods and experimental data are available, we find that, with very few exceptions, our method yields a level of agreement with the experimental data which is comparable to or better than the predictions from the other two methods.

Quantum state reconstruction based on weak continuous measurement has the advantage of being fast, accurate, and almost non-perturbative. In this work we present a pedagogical review of the protocol proposed by Silberfarb et al., PRL 95 030402 (2005), whereby an ensemble of identically prepared systems is collectively probed and controlled in a time-dependent manner so as to create an informationally complete continuous measurement record. The measurement history is then inverted to determine the state at the initial time through a maximum-likelihood estimate. The general formalism is applied to the case of reconstruction of the quantum state encoded in the magnetic sublevels of a large-spin alkali atom, 133Cs. We detail two different protocols for control. Using magnetic interactions and a quadratic ac-Stark shift, we can reconstruct a chosen hyperfine manifold F, e.g., the 7-dimensional F=3 manifold in the electronic-ground state of Cs. We review the procedure as implemented in experiments (Smith et al., PRL 97 180403 (2006)). We extend the protocol to the more ambitious case of reconstruction of states in the full 16-dimensional electronic-ground subspace (F=3 \oplus F=4), controlled by microwaves and radio-frequency magnetic fields. We give detailed derivations of all physical interactions, approximations, numerical methods, and fitting procedures, tailored to the realistic experimental setting. For the case of light-shift and magnetic control, reconstruction fidelities of \sim 0.95 have been achieved, limited primarily by inhomogeneities in the light shift. For the case of microwave/RF-control we simulate fidelity >0.97, limited primarily by signal-to-noise.