A spectral line emitted by neutral hydrogen having a frequency of 1420 megahertz and a wavelength of 21 centimeters; radiation from this line is used in radio astronomy to study the amount and velocity of hydrogen in the Galaxy. McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyri...
Thus if the Universe was very dense in its first few minutes, most of the deuterium would have been converted to helium. Deuterium is not easy to detect but recent measurements of the ratio of deuterium to hydrogen give an upper limit of about 2 × 10–5 for interstellar gas. Hydrogen ...
The equilibrium ratio of ortho- to para-hydrogen depends on temperature. At room temperature or warmer, equilibrium hydrogen gas contains about 25% of the para form and 75% of the ortho form.[30] The ortho form is an excited state, having higher energy than the para form by 1.455 kJ/...
Precision experiments at the antiproton decelerator have recently constrained the properties of the antiproton through studies in Penning traps21, 22 or with antiprotonic helium23. For example, the antiproton charge-to-mass ratio is known to agree with that of the proton to 69 parts per trillion...
Thus if the Universe was very dense in its first few minutes, most of the deuterium would have been converted to helium. Deuterium is not easy to detect but recent measurements of the ratio of deuterium to hydrogen give an upper limit of about 2 × 10–5 for interstellar gas. Hydrogen ...
The most accurate measurement of the antiproton-to-electron mass ratio is performed using two-photon spectroscopy of antiprotonic helium [22]. The experimental result gives 𝑚𝑝¯/𝑚𝑒=1836.1526736(23)mp¯/me=1836.1526736(23) which agrees within uncertainty with the proton-to-electron mas...
To achieve net-zero objectives, the expansion of renewable energy sources is anticipated to be accompanied by an increased use of carbon-free fuels, such as hydrogen. Internationally, there are proposals for transporting hydrogen by synthesizing it into