Cancellation Of Systematic Errors Research Articles

Double-β-decayQvalues ofSe74andGe76

The atomic masses of $^{74}\mathrm{Ge}$, $^{74}\mathrm{Se}$, $^{76}\mathrm{Ge}$, and $^{76}\mathrm{Se}$ have been determined from cyclotron frequency ratios of pairs of ions simultaneously trapped in a cryogenic Penning trap. Allowing for cancellation of systematic errors in the mass differences between isobars, we determine the $Q$ value for double-electron capture of $^{74}\mathrm{Se}$ to be 1209.240(7) keV, and the $Q$ value for double-electron emission of $^{76}\mathrm{Ge}$ to be 2039.061(7) keV. The new ${Q}_{2\mathrm{EC}}$ value for $^{74}\mathrm{Se}$ precludes a large resonant enhancement for neutrinoless double-electron capture.

Masses ofTe130andXe130and Double-β-DecayQValue ofTe130

The atomic masses of 130Te and 130Xe have been obtained by measuring cyclotron frequency ratios of pairs of triply-charged ions simultaneously trapped in a Penning trap. The results with one standard deviation uncertainty are M(130Te) = 129.906 222 744(16) u and M(130Xe) = 129.903 509 351(15) u. Allowing for cancellation of systematic errors in the mass difference, the double-beta-decay Q-value, required for searches for the neutrino-less double-beta-decay of 130Te, is determined to be Qbb (130Te) = 2527.518(13) keV.

Accuracy of typical approximations in classical models of intermolecular polarization

One of the largest limitations of standard molecular-mechanics force fields is the neglect of intermolecular polarization. Several attempts to cure this problem have been made, but the results have not always been fully satisfactory. In this paper, we present a quantitative study of the fundamental approximations that underlie polarization models for classical force fields. The induced charge density of a large set of molecular dimers is compared to supermolecular calculations for a hierarchy of simplified models. We study the effect of the Pauli principle, the local inhomogeneity of the electric field, the intramolecular coupling of the polarization response, and the fact that the induced density is a continuous function. We show that standard point-polarizability models work rather well, despite their lack of all these effects, because (1) there is a systematic error cancellation between the neglect of effects of the Pauli principle and the locally inhomogeneous electric field, and (2) the lack of intramolecular coupling and the use of a dipole expansion of the induced density have only minor effects on the polarization. However, the cancellation in (1) is not perfect, and therefore polarizable force-fields could be improved if both effects are explicitly treated.

A compact solenoid 3He neutron spin filter with a fast spin flip capability

We have designed and demonstrated a compact solenoid 3He neutron spin filter with a fast spin flip capability. The 3He spin is flipped by adiabatic fast passage (AFP) in a short time and with very little polarization loss, which is essential for polarized neuron scattering measurements in cancellation of systematic errors. A solenoid coil and compensation coils provide a uniform magnetic field for the polarized 3He to minimize the longitudinal spin relaxation. This neutron spin filter can be installed rather easily in neutron scattering spectrometers as a neutron polarizer as well as a neutron spin analyzer. We describe the design and the performance of the device tested by AFP-NMR and with a pulsed neutron beam at KEK.

Implementation of a three-quantum-bit search algorithm

We report the experimental implementation of Grover’s quantum search algorithm on a quantum computer with three quantum bits. The computer consists of molecules of C13-labeled CHFBr2, in which the three weakly coupled spin-1/2 nuclei behave as the bits and are initialized, manipulated, and read out using magnetic resonance techniques. This quantum computation is made possible by the introduction of two techniques which significantly reduce the complexity of the experiment and by the surprising degree of cancellation of systematic errors which have previously limited the total possible number of quantum gates.

Observation of the Holstein shift in high- Tc superconductors with thermal-modulation reflectometry

We use the experimental technique of thermal-modulation reflectometry to study the relatively small temperature dependence of the optical conductivity of superconductors. Due to a large cancellation of systematic errors, this technique is shown to be a very sensitive probe of small changes in reflectivity. We analyze thermal-modulation reflection spectra of single crystals and epitaxially grown thin films of YBa 2Cu 3O 7−δ and obtain the α t r 2 F(ω) function in the normal state, as well as the superconductivity-induced changes in reflectivity. We present detailed model calculations, based on the Eliashberg-Migdal extension of the BCS model, which show good qualitative and quantitative agreement with the experimental spectra.

PM3 study of the proton affinities of 2‐, 3‐, and 4‐monosubstituted pyridines in the gas phase

AbstractHeats of formation (ΔHf) and proton affinities (PA) of 2‐, 3‐, and 4‐monosubstituted pyridines in the gas phase are calculated using the AM1 and PM3 semiempirical methods. The following substitutents are considered: NO2, CN, CF3, CHO, F, Cl, COCH3, H, CH3, OCH3, SCH3, NH2, and N(CH3)2. The results are compared with the experimental data. Both methods reproduce the ΔHf with comparble accuracy; the rms deviations are 4.1 (AM1) and 4.5 kcal/mol (PM3) for the free bases and 9.5 (AM1) and 9.7 kcal/mol (PM3) for their conjugated acids. The PA are systematically underestimated by both methods, but AM1 appears to be clearly better than PM3 for reproducing the experimental values. The rms deviations for AM1 and PM3 are 5.1 and 9.6 kcal/mol, respectively. This is due to a cancellation of systematic errors in the calculated ΔHf in the AM1 case and to a summation of the errors in the PM3 case. Both methods correctly reproduce conformations of the molecules under consideration.

Liquid GeBr4. I. A test of the anomalous x-ray scattering method as applied to disordered materials

This study tested the accuracy of the anomalous x-ray scattering technique as part of an investigation of the molecular liquid GeBr4. The differential anomalous scattering technique proved to be quite accurate, giving nearest-neighbor coordination distances and numbers correct to 0.02 Å and 4%, respectively, as compared with known values. The high accuracy of the approach evidently depends on a cancellation of systematic errors when subtracting data sets at two nearby photon energies. The straightforward three-wavelength approach to determining the partial-distribution functions is quite ill conditioned and small experimental errors cause large errors in the resulting partial distribution functions. An alternate procedure, suggested by Munro, uses differences to determine the partial distribution functions (PDF’s) and hence takes advantage of the cancellation of systematic errors. This approach yields Br–Br, Ge–Br, and Ge–Ge PDF’s with error levels of approximately 5%–10%, 30%, and 100%, respectively. Singular value decomposition of the weighting matrix can be used to predict the relative accuracies of the three PDF’s before experimentation.

Analysis of error in the determination of respiratory gas exchange at varying FIO2.

On-line gas exchange monitors have been based on the measurement of both inspired and expired flows (method A) or on the measurement of expired flow only (method B). In both methods, the cancellation of systematic errors is appreciable if calibration errors in the inspiration variables are matched with calibration errors in the corresponding expiration variables. The determination of oxygen consumption (VO2) results in a considerable amplification of random measurement error, which becomes larger as the inspired oxygen fraction (FIO2) is made larger. For example, when in method A all gas compositions and flows are in error by +/- 0.01, the computed value of VO2 will be in error by +/- 0.16 when FIO2 = 0.21 and by +/- 0.40 if FIO2 = 0.50. When air is breathed, method B creates smaller errors than method A, but as FIO2 is increased the error in method B increases sharply and eventually overtakes that of method A. Even at high FIO2 values, the random error in VO2 may be reduced to an acceptable value by estimating it from a sequence of 100 measurement samples requiring a minimum of 5 min to acquire. There is no error amplification in the computation of carbon dioxide production.