{"id":292512,"date":"2025-11-15T04:36:07","date_gmt":"2025-11-15T04:36:07","guid":{"rendered":"https:\/\/www.newsbeep.com\/us\/292512\/"},"modified":"2025-11-15T04:36:07","modified_gmt":"2025-11-15T04:36:07","slug":"hd%e2%81%ba-ions-cooled-to-18-mk-yield-most-precise-vibrational-rotational-spectra-to-date","status":"publish","type":"post","link":"https:\/\/www.newsbeep.com\/us\/292512\/","title":{"rendered":"HD\u207a ions cooled to 18 mK yield most precise vibrational-rotational spectra to date"},"content":{"rendered":"

\"Researchers<\/p>\n

Synergistically cooled Be\u207a-HD\u207a ion crystal and molecular dynamics simulation. Credit: APM<\/p>\n

A research team from the Innovation Academy for Precision Measurement Science and Technology (APM) of the Chinese Academy of Sciences has made significant progress in precisely measuring the vibrational-rotational spectra of hydrogen molecular ions (HD\u207a).<\/p>\n

The researchers prepared a Be\u207a-HD\u207a two-component ion Coulomb crystal at millikelvin temperatures in a linear ion trap. They developed an innovative quantum state preparation and spatially resolved fluorescence detection techniques and used these to measure the high-resolution vibrational-rotational transition spectra of HD\u207a molecular ions. Their findings were published<\/a> in Physical Review A.<\/p>\n

HD\u207a is the simplest heteronuclear molecular ion, composed of one proton, one deuteron, and one electron. Its vibrational-rotational transition energies can be precisely calculated, making it an ideal system for testing quantum electrodynamics (QED) theory and determining fundamental physical constants<\/a>, such as the proton-electron mass ratio.<\/p>\n

To minimize the effects of Doppler broadening on their measurements, the researchers employed laser-cooled beryllium ions to cool the HD\u207a ions, reducing their temperature to 18 millikelvins (mK). To address the low population of HD\u207a molecules in the vibrational-rotational ground state (v = 0, N = 0), they employed the resonance-enhanced threshold photoionization (RETPI) technique to prepare HD\u207a ions precisely in the vibrational-rotational ground state. This technique achieved an initial quantum state population degree of 93%.<\/p>\n

\"Researchers<\/p>\n

Vibrational-rotational transition spectrum with resolved hyperfine structure of HD\u207a. Credit: APM<\/p>\n

Compared with traditional cryogenic cooling or optical pumping methods, this technique significantly increases the ground-state population rate, laying a solid foundation for subsequent high-resolution transition detection.<\/p>\n

Additionally, in the two-component ion crystal, HD\u207a ions appear as non-fluorescent “dark ions,” and the change in the number of HD\u207a ions during resonant dissociation is the key to spectral measurement. To address this issue, the researchers developed a spatially resolved fluorescence collection technique using a high-sensitivity, electron-multiplying intensified CCD (EMICCD) camera. This setup enabled the real-time acquisition of ion crystal images and the real-time, non-destructive measurement of HD\u207a ion numbers.<\/p>\n

Using these innovative methods, the researchers measured, for the first time, the vibrational-rotational transition spectrum of HD\u207a ions (v,N):(0,0)\u2192(6,1). The transition frequency value is 303,396,506.7(20) MHz, with a relative accuracy reaching parts per billion (ppb), which is consistent with the current most precise QED theoretical prediction.<\/p>\n

Combining theoretical calculations, they further deduced that the value of the proton-electron mass ratio (\u03bcpe) is 1836.152648(45). This value aligns with the 2022 recommended value from the International Council for Science: Committee on Data for Science and Technology.<\/p>\n

More information:
\n\t\t\t\t\t\t\t\t\t\t\t\tQian-Yu Zhang et al, Rovibrational spectroscopy of state-selected HD+ ions through spatially resolved fluorescence collection, Physical Review A (2025). DOI: 10.1103\/qxyn-jx1t<\/a><\/p>\n

\n\t\t\t\t\t\t\t\t\t\t\t\t\tProvided by
\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\tChinese Academy of Sciences<\/a>
\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<\/p>\n

\t\t\t\t\t\t\t\t\t\t\t\t\t\t<\/a>\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<\/p>\n

\n\t\t\t\t\t\t\t\t\t\t\t\tCitation:
\n\t\t\t\t\t\t\t\t\t\t\t\tHD\u207a ions cooled to 18 mK yield most precise vibrational-rotational spectra to date (2025, November 14)
\n\t\t\t\t\t\t\t\t\t\t\t\tretrieved 14 November 2025
\n\t\t\t\t\t\t\t\t\t\t\t\tfrom https:\/\/phys.org\/news\/2025-11-hd-ions-cooled-mk-yield.html\n\t\t\t\t\t\t\t\t\t\t\t <\/p>\n

\n\t\t\t\t\t\t\t\t\t\t\t This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no
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