Figure. Sensing the difference of gravity in 1mm altitude change on Earth using an SXWG and 45Sc nuclear clock transition.
替地球重力拍X光影像
Phys. Rev. Research 7, 013158
Shin-Yu Lee, Sven Ahrens, and Wen-Te Liao
Gravitationally sensitive structured x-ray optics using nuclear resonances
我們與上海師範大學的Sven Ahrens教授合作設計一種新型結構化X光波導管[structured X-ray waveguide (SXWG)]，能探測地球上1毫米高度變化所引起的重力差異。根據X光通過波導管傳播行為與量子粒子行為之間的類比，我們在光學薛丁格方程式的引導下設計了SXWG，將鈧-45-碳交錯的週期性結構夾在兩個鉑包覆層之間。其中鈧-45同位素的極窄原子核鐘躍遷，其自然線寬約為2 Hz，躍遷能量約為12.4 keV。如此窄的線寬能用來檢測到鈧-45與共振X光之間在1毫米高度變化下的微小交互作用差異。因此改變SXWG的高度將因重力紅位移效應而改變兩個X光波導管模態之間的耦合強度。我們的計算結果顯示，SXWG的X光輸出光班分佈會受到高度變化的影響。故透過檢視光班的變化便能得知SXWG與X光光源之間的高度差。而使用其他同位素，如釷-229、銀-109等，甚至可以達到微米等級的靈敏度。
We collaborate with Prof. Sven Ahrens from Shanghai Normal University to design a novel structured X-ray waveguide (SXWG) capable of detecting gravitational differences caused by height changes as small as 1 millimeter on Earth. Based on an analogy between the propagation of X-rays through a waveguide and the behavior of quantum particles, we designed the SXWG under the guidance of the optical Schrödinger equation, sandwiching a periodic structure of 45Sc scandium-carbon interleaved layers between two platinum-coated layers. The scandium isotope has an extremely narrow nuclear clock transition, with a natural linewidth of about 2 Hz and a transition energy of approximately 12.4 keV. Such a narrow linewidth can be used to detect tiny interaction differences between 45Sc and resonant X-rays under a 1-millimeter height change. Thus, altering the height of the SXWG will change the coupling strength between two X-ray waveguide modes due to the gravitational redshift effect. Our calculations show that the X-ray output intensity distribution of the SXWG is affected by height changes. Therefore, by examining the changes in the light pattern, the height difference between the SXWG and the X-ray source can be determined. Using other isotopes, such as 229Th or 109Ag, can even achieve sensitivity at the micrometer level.