Absorption coefficients of the negative helium ion

Helium Absorption by Protogalactic Gas

We present a new, high resolution HST/GHRS spectrum of quasar Q0302003, and use the He Lyman-α absorption, together with a high resolution Keck spectrum of the HI Lyman-α forest, to probe the distribution and ionization state of the protogalactic foreground gas at z ≈ 3.3. Within ≈ 4000 km/sec of the quasar redshift the spectrum shows a substantial flux (τ ≈ 1) with “He Lyman-α forest” absorpti...

Observation of a New Type of Negative Ion in Superfluid Helium

In recent work, we have developed a new technique for the study of the properties of electron bubbles (negative ions) in liquid helium. We use ultrasound to measure the critical negative pressure Pc at which an electron bubble becomes unstable and explodes. The value of Pc is affected, for example, by the quantum state of the electron and is reduced if the bubble is attached to a quantized vort...

Coefficients of the second viscosity in thin liquid-helium films.

Coefficients of the second viscosity in bulk liquid helium.

Fluorescence polarization of helium negative-ion resonances excited by polarized electron impact

We have investigated helium (1s3d) 3D → (1s2p) 3P (588 nm) fluorescence produced by electron impact excitation in the vicinity of the (2s22p) 2P and (2s2p2) 2D negative-ion resonances at 57.2 and 58.3 eV, respectively. In contrast to previous work, we use spin-polarized incident electrons and report the relative Stokes parameters P1, P2 and P3 in the 55–60 eV region. Our failure to see discerna...