Instantaneous Clear Sky Radiative Forcings of Halogenated Gases

The clear sky instantaneous radiative forcings of the 14 halogenated gases previously shown to have the largest contribution to global warming, were found. The calculation used the absorption cross sections for the halogenated gases which are assumed to be independent of temperature as well as over 1/3 million line strengths for the 5 naturally occurring greenhouse gases: H$_2$O, CO$_2$, O$_3$, CH$_4$ and N$_2$O, from the Hitran database. The total radiative forcing of the halogenated gases at their 2020 concentrations is 0.52 (0.67) W/m$^2$ at the tropopause (mesopause). Over half of this forcing is due to CFC11 and CFC12 whose concentrations are declining as a result of the Montreal Protocol. The rate of total forcing change for all 14 halogenated gases is 1.5 (2.2) mW/m$^2$/year at the tropopause (mesopause). The calculations assumed a constant altitude concentration for all halogenated gases except CFC11, CFC12 and SF$_6$. Using the observed altitude dependence for those 3 molecules reduced their radiative forcings by about 10%. The global warming potential values were comparable to those given by the Intergovernmental Panel on Climate Change. The contribution of a gas to global warming was estimated using the forcing power per molecule defined as the derivative of its radiative forcing with respect to its column density. For the present atmosphere, the per-molecule forcing powers of halogenated gases are orders of magnitude larger than those for the 5 naturally occuring greenhouse gases because the latter have much higher concentrations and are strongly saturated. But, the rates of concentration increase of the 5 main greenhouse gases are orders of magnitude greater than that of any halogenated gas. Assuming the temperature increase caused by each gas is proportional to its radiative forcing increase, the 14 halogenated gases are responsible for only 2% of the total global warming.Comment: arXiv admin note: text overlap with arXiv:2103.16465, arXiv:2006.0309

Deuterium Lamb shift via quenching-radiation anisotropy measurements

The Lamb shift of a hydrogenic ion can be deduced from the anisotropy in the angular distribution of the 2s12-1s12 electric field quenching radiation. The accuracy of our previous anisotropy measurement for deuterium is improved to about ± 150 ppm. The derived Lamb shift is (1059.36±0.16) MHz. The sources of error are carefully analyzed and the prospects for further improvements in the accuracy are discussed. © 1978 The American Physical Society

Measurements of an e 1-M 1 interference effect in the electric-field quenching of spin-polarized He+2s12 ions

When a beam of spin-polarized metastable He+2s12 ions is quenched by an electric field E, the emitted radiation intensity contains an asymmetry term which is proportional to kE ×P, where P is the spin-polarization vector and k is the direction of observation. The effect is due to interference between spontaneous magnetic-dipole (M 1) and induced electric-dipole (E 1) decay modes to the ground state. At |E|=38.14 V/cm, the measured asymmetry is (0.3230.085) × 10-3 in agreement with the theoretical value 0.3443 × 10-3. The experiment provides the first measurement of the relativistic M 1 matrix element for the 2s12-1s12 transition in a hydrogenic ion. The paper contains an extensive discussion of all possible asymmetry effects, including higher-order relativistic and electric-field perturbation corrections. © 1982 The American Physical Society

Measurement of the n=2 Lamb shift in He+ by the anisotropy method

A high-precision measurement of the 2s 2S1/22p 2P1/2 Lamb shift in He+ by the quenching-anisotropy method is reported. The theory and experimental method are described in detail. The measured value of 14042.520.16 MHz (11 parts per million) rivals the accuracy of Lamb-shift measurements in hydrogen by microwave resonance. By subtracting the known low-order terms in the Lamb shift, we interpret the results as a measurement of the order (Z)6mc2 and higher contributions to the electron self-energy GSE(Z). The various contributions to the Lamb shift are discussed, and a revised value for GSE(Z) at low Z is extracted from high-Z calculations. The theoretical value for the Lamb shift is 14042.510.2 MHz, in excellent agreement with experiment. The results provide the most sensitive available determination of GSE(Z) for low Z. Measurements and calculations for hydrogen and other members of the isoelectronic sequence are discussed. © 1991 The American Physical Society

Asymmetry measurement of the 2s1/2(hy1s1/2 relativistic magnetic-dipole matrix element in He+

When a beam of spin-polarized He+(2s1/2) ions is quenched by an electric field E, the emitted radiation intensity contains a left-right-asymmetry term proportional to Pk×E, where P is the spin-polarization vector and k is the observation direction. The resulting asymmetry is proportional to the relativistic magnetic dipole matrix element 1s1/2,1/2M1,02s 1/2,1/2. The measured asymmetry (2.935±0.337)×10-4 corresponds to the matrix element 1s1/2,1/2M1,02s 1/2,1/2 =-(0.2725±0.0313)α2eLatin small letter h with stroke/mc, in agreement with the theoretical value -0.2794α2eLatin small letter h with stroke/mc. The measurement provides a direct test of the relativistic corrections to the magnetic dipole transition operator. © 1986 The American Physical Society

He+ 2p state lifetime by a quenching-asymmetry measurement

An interference asymmetry in the angular distribution of the Ly quenching radiation emitted by He+ ions in the metastable 2s1/2 state is measured to high precision to obtain the lifetime of the 2p1/2 state. The derived lifetime of (0.997 170.000 75)×10-10 s is the most accurate available for a fundamental atomic system. A detailed discussion of systematic corrections is included. The result is in good agreement with theory, thereby confirming the theory of radiative transition probabilities to 0.075%, and indicating that differences between theory and experiment for the alkali metals must be due to either inadequate wave functions or experimental errors. © 1992 The American Physical Society

Improved anisotropy measurement of the Lamb shift in He+

An improved anisotropy measurement of the Lamb shift is obtained by means of a new method for the high-precision measurement of light intensities. The photon-counting techniques used in our previous work [Phys. Rev. A 20, 1299 (1979)] are replaced by the direct measurement of photoelectron currents with high-precision electrometers. Our new value for the Lamb shift in He+ is 14 041.91.5 MHz. This agrees with the earlier microwave resonance measurement of Lipworth and Novick [Phys. Rev. 108, 1434 (1957)], but lies clearly below the more recent measurement by Narasimham and Strombotne [Phys. Rev. A 4, 14 (1971)]. © 1987 The American Physical Society

Lamb shift in He+: Resolution of a discrepancy between theory and experiment

The Lamb shift in helium ions were investigated to verify or remove a discrepancy between theory and experiment by the anisotropy method. The method was used for the elimination of residual polarization sensitivity of the photon detectors. The results showed that the experimental value of a Lamb shift were in agreement with the theoretical values

Lifetime of the 2p state in He II

When a beam of spin-polarized metastable He+(2s12) ions is quenched by an electric field E\u27, the emitted radiation intensity contains an asymmetry term proportional to (kE)(P\u27k×E), where P\u27 is the spin-polarization vector and k is the direction of observation. The resulting asymmetry is nearly proportional to the level width of the 2p12 state in He+. The measured asymmetry 0.007 602 70.000 020 3 corresponds to a lifetime 2p=(0.99920.0026)×10-10 sec, in fair agreement with the theoretical value 2p=0.9972×10-10 sec. © 1983 The American Physical Society