AGOGO DA AKA DAIDAITA DA ƘWAYAR ATOM YA YI AIKI NA SA'O'I 30

Agogo mafi daidaito a duniya suna ƙirga motsin kai da komowar electron a cikin atom, wanda ake leƙawa da laser. Suna aiki a matsayin ma’aunin mita ga ilimin aune-aune (metrology) da gwaje-gwajen kimiyyar lissafi ta asali. Thorium-229 yana ba da wani irin pendulum daban: ƙwayar tsakiyarsa (nucleus) tana da wani yanayi da aka tayar, wanda ake kira isomer, wanda ke sama da yanayinsa na ƙasa da kusan electronvolt 8.4 kawai — ƙasa da isa har laser zai iya kaiwa. Hasken da ake buƙata yana cikin vacuum ultraviolet, a nanomita 148.4.

A cewar marubutan, agogon da aka gina a kan wannan sauyin nukiliya zai kasance mai matuƙar jin yiwuwar sauye-sauyen mu’amaloli na asali, kuma zai iya taimakawa wajen neman dark matter. Saka thorium a cikin crystal mai haske na calcium fluoride yana ba da adadi mai yawa na ƙwayoyin tsakiya masu sha a cikin ƙaramin ɗan abu mai ƙarfi: hanyar agogon nukiliya mai ƙarfi (solid-state).

Ba na farko ba, amma mafi daɗewa a nan

Takardar tana mai da hankali kan abin da aka riga aka yi. Bayanan tunaninta sun lissafa nuclear fluorescence, tayarwa kai tsaye da laser, comb spectroscopy, laser na ultraviolet mai ci gaba, absorption spectroscopy har ma da zagayen martani na nukiliya (nuclear feedback loops) da wasu tawagogi suka ruwaito. Abin da wannan aikin ya ƙara shi ne agogo da ke aiki na dogon lokaci a kan wani crystal, da haɗi mai kyau tsakanin bakan da aka auna da mitar da agogon ke bayarwa a zahiri.

Sha shi ne mabuɗi. Maimakon jiran ƙwayoyin tsakiya da aka tayar su ruguje — wani tsari mai jinkiri — tawagar tana auna yawan hasken da crystal ɗin ke haɗiye. Hakan yana ba da sigina mai sauri da ke faɗin ko laser ɗin yana kan layin ko a gefensa.

Ninkawa uku don isa ga ƙwayar tsakiya

Pengfei Wang, Xu-Fei Yin, Yu-Ao Chen da abokan aikinsu a Jami’ar Kimiyya da Fasaha ta China, tare da abokan aiki a Chinese Academy of Sciences da TU Wien a Vienna, sun fara daga laser na infrared a nanomita 1,187, wanda aka daidaita a kan wani optical cavity mai matuƙar kwanciyar hankali. Ninkawar mita uku a jere tana mayar da shi zuwa 594, sannan 297, sannan nanomita 148.4. Sannan kusan picowatt 750 na hasken ultraviolet suna ratsa wani guntun crystal da aka saka wa thorium mai kauri milimita 1.8, wanda aka yanka daga wani crystal mai suna X2. An auna wasu guntayen X2 a Vienna da JILA.

A cikin crystal ɗin, filin lantarki na wurin yana raba layin nukiliyar zuwa sassa da dama. A wani nau’in wurin thorium, tawagar ta bambance huɗu daga cikinsu, tare da wani faɗaɗɗen resonance daga nau’in wuri na biyu. Layi mafi ƙarfi kuma mafi siriri, wanda ake kira b, yana da faɗin kilohertz 83 kawai — a kan mita na kusan hertz tiriliyan dubu biyu.

Sa’o’i talatin a kan layi ɗaya

Don gudanar da agogon, tsarin yana leƙa gefunan layi b biyu kuma yana ɗan tura mitar laser kusan kowace daƙiƙa 10. Wani frequency comb, wanda aka danganta da hydrogen maser da aka daidaita da agogon atom na strontium, yana auna abin da ake fitarwa.

• Zagayen ya riƙe na sa’o’i 30 — zagayen aune-aune 1,061,000, waɗanda 29 kawai aka ƙi.
• Tawagar ta dakatar da gudanarwar yayin da agogon yake manne har yanzu: yawan photon ya faɗi daga miliyan 5.79 zuwa 2.41 a daƙiƙa, abin da marubutan suka danganta ga fitar iska (outgassing) da ke lalata wucewar ultraviolet.
• Mitar layi b da aka auna: kilohertz 2,020,407,298,796.17, da rashin tabbas na kilohertz 0.13.
• Kwanciyar hankalinta tana inganta da lokacin matsakaici kuma ta kai 1.24 × 10⁻¹³ bayan daƙiƙa 10,000.
• Gudanarwa ta biyu ta sa’o’i 6.6 a kan wani sashe, layi c, ita ma ta yi aiki.

Wuraren layukan da aka karanta daga bakan sha da mitocin da agogon ya bayar sun yi daidai a cikin rashin tabbas ɗinsu. Lokacin da tawagar ta sake fara agogon sau uku ƙari, bayan buɗe ɗakin da sake daidaita na’urorin haske, matsakaicin mitocin sun bazu a cikin kilohertz 1.6.

Crystal ɗaya, dakunan gwaje-gwaje uku

Ta hanyar kwatanta guntunsu da guntayen crystal guda da aka auna a Vienna da JILA, bayan gyara don zafi, tawagar ta sami tsarin layuka iri ɗaya. Wasu bambance-bambance sun rage: layi b yana sama da ƙimar Vienna da kilohertz 11.6 kuma sama da ta JILA da 6.6; layi c kusan kilohertz 30 sama da duka biyun. Marubutan har yanzu ba za su iya faɗin ko waɗannan sun fito daga sauran kurakuran zafi ba, karkacewa a cikin mannewa (locking), ko ainihin bambance-bambance tsakanin samfuran.

Nesa da layin ƙarshe

Lambobin suna buƙatar mahallin, kuma takardar ta bayar da shi. Kwatancen da ke tsakanin hydrogen maser da agogon strontium da aka yi amfani da shi a matsayin ma’auni shi kansa ya fi agogon thorium kwanciyar hankali fiye da ninki goma a cikin lokutan matsakaici iri ɗaya. Lissafin rashin tabbas a fili bai cika ba, kuma ba a naɗi zafi ba a cikin sa’o’i 14.7 na farko na dogon gudanarwar. Darajar wannan aikin tana cikin juriya da duba juna: sauyin nukiliya, da aka riƙe fiye da kwana ɗaya, aka kwatanta shi da guntayen crystal guda a dakunan gwaje-gwaje uku.