KA HASKA HASKEN DA YA DACE, KUSAN BABU ELECTRON DA ZAI FITO

Lokacin da haske ya bugi abu, zai iya ɓalle electrons: da zarar photon ya kawo ƙarfi (energy) fiye da ƙarfin da ke riƙe da electron, electron ɗin zai iya fita, kuma sama da wannan iyaka yawan fitowar gabaɗaya yana kasancewa sama da sifili. Amma fiye da shekaru sittin da suka wuce, J. W. Cooper ya yi hasashen cewa a wasu matakan ƙarfi wannan yawan fitowa zai iya dannewa. Yanzu ana kiran wannan raguwar ƙasan Cooper (Cooper minimum).

Raguwar da ba ta taɓa kaiwa sifili

Ana bayyana electron da ke tserewa a matsayin igiya (wave), kuma damar tserewarsa ta dogara ne da yadda wannan igiyar da ke fita ta haɗu (overlap) da orbital ɗin da ya tashi daga ciki. Wannan haɗuwa tana tara ɓangarori na ƙari da na ragi. A wani takamaiman gudun electron ɗin da ke tafiya, jimillar tana sauya alama — tana wucewa ta sifili a kan hanya.

A wajen zarra, an ga ƙasan Cooper a cikin ’yan tsare-tsare kaɗan kawai, dukkansu har yanzu masu kama da zarra, kuma a can yawan fitowar yana raguwa ne kawai. Electron ɗin yana fita ta hanyoyi da dama, da ake kira igiyoyin ɓangare (partial waves), kuma da wuya sosai dukansu su wuce sifili a daidai matakin ƙarfi ɗaya.

Akwai keɓantacce ɗaya. Electron da ke cikin orbital s na zarra, wanda yake zagaye cikakke, zai iya fita ta hanya ɗaya kawai, “igiyar p” (p-wave), saboda ƙa’idodin da ke tafiyar da yadda ake shanye haske. Hanya ɗaya, jimilla ɗaya: idan ta wuce sifili, babu abin da ke fitowa. A cewar marubutan, wannan “fitar electron sifili ta haske” (zero photoemission) ba kasafai ake samunta ba ko da a cikin zarra, kuma ba a taɓa ba da rahotonta a wajensu ba.

Zarra da aka yi da zarra 13

Yuta Suzuki, Mamoru Tanaka, Akira Terasaki da Takuya Horio na Jami’ar Kyushu, tare da Yoshi-ichi Suzuki na Health Sciences University of Hokkaido, sun gina irin wannan orbital mai zagaye da gangan, a cikin wani babban zarra (superatom): tarin zarra da ke kwaikwayon zarra ɗaya. Electrons ɗinsa suna cika matakai (shells) da ake yi wa lakabi 1S, 1P, 1D, 2S, kwatankwacin 1s, 2s, 2p na zarra na yau da kullum.

Ɗan takararsu shi ne Ag12W⁻: zarran azurfa goma sha biyu da suka yi keji mai siffar icosahedron (siffa mai fuskoki 20) — tsari mafi daidaito da tari mai iyakataccen girma zai iya samu — a kewayen zarran tungsten ɗaya, tare da ƙarin electron ɗaya. A baya ƙungiyar ta gano cewa irin waɗannan kejin da aka gina a kewayen vanadium, niobium ko tantalum suna da matakai cikakku. Tungsten, daga shafi na gaba a teburin abubuwa (periodic table), yana ƙara ƙarin electron ɗaya. Yana zaune shi kaɗai a matakin 2S: zagaye, kamar orbital s na zarra, amma ya bazu a kan dukan tarin.

Lissafi sun tabbatar da cewa icosahedron ita ce siffa mafi kwanciyar hankali. Electrons da aka ciro daga Ag12W⁻ suna samar da kololuwar ƙarfi ɗaya mai kaifi, kusa da iyakar tantancewar na’urar: kejin da ƙyar yake sauya tsari lokacin da electron ya fita (da ya sauya siffa, wani ɓangare na ƙarfin zai tafi wajen girgiza shi, ya bazar da kololuwar). Tsarinsu yana kama sosai da na ion ɗin azurfa shi kaɗai, Ag⁻, wanda electron ɗinsa na waje ke zaune a cikin orbital s mai zagaye.

Hotuna hamsin da biyar, da wani giɓi

Ƙungiyar ta samar da tarin a cikin iskar gas, ta ware su bisa nauyi (mass) kuma ta harba musu laser mai sauyawa, tana kama electrons da ke tserewa a kan kyamara. Sun ɗauki hotuna 55, da ƙarfin photon daga electronvolt 1.46 (ma’aunin ƙarfi da ya dace da ƙananan ƙwayoyi guda-guda), wato iyakar ɓallewa, har zuwa 4.00.

Electrons da ke tserewa daga Ag12W⁻ yayin da ƙarfin laser ke hawa: zoben yana dusashewa tsakanin kusan 2.11 da 2.48 eV, sannan ya dawo. Layuka biyu na farko kowanne yana da ma’aunin haskensa; layukan da ke ƙasa suna raba na uku. — Hoto na 3, Suzuki da abokan aiki (2026), arXiv:2610.32031.

Yayin da ƙarfin ke hawa, wani zobe na electrons yana girma. Sannan, daga electronvolt 2.11 zuwa 2.48, ya zama kusan ba a iya ganinsa. Wani gwaji mai zaman kansa, wanda ke ƙirga yawan tarin da suka tsira daga laser a cikin tarkon ion (ion trap), ya yarda da haka: ɓallewa tana zama kusan sifili tsakanin electronvolt 2.0 da 2.5. Tsakiyar giɓin tana kusa da electronvolt 2.3, inda electron da ke tserewa zai ɗauki kusan electronvolt 0.85 na ƙarfin motsi (kinetic energy) (2.3 a cire 1.46 da aka kashe don ɓalle shi).

Rabi biyu da ke soke juna

Marubutan sun lissafa haɗuwar da ke zuciyar wannan tsari: orbital ɗin tarin, sau igiyar da ke fita, sau kubin nisa daga tsakiya. A electronvolt 0.85, ɓangarorin ƙari da na ragi na wannan sakamakon ninkawa “suna soke juna daidai, suna ba da haɗaka (integral) ta sifili”.

Ƙa’idar, an nuna ta a kan ƙwallo na zato maimakon ainihin tarin: a wani matakin ƙarfin electron ɗaya (1.87 eV a cikin wannan sauƙaƙan samfuri), ɓangarorin ƙari (ja) da na ragi (shuɗi) na haɗuwar suna soke juna, kuma fitowar tana ɓacewa. — Hoto na 1, Suzuki da abokan aiki (2026), arXiv:2610.32031.

Alama ta biyu ita ce alkiblar da electrons ke fita, wadda ake taƙaitawa da lamba ɗaya, β, wadda take 0 idan electrons suna fita daidai a kowace alkibla, kuma 2 idan galibi suna fita a alkiblar da filin lantarki (electric field) na hasken laser ke jujjuyawa. Tana kaiwa 2, iyakar da ake tsammani ga zarra, a kusan electronvolt 2.7 da kuma daga 3.3 zuwa 4.0; wani tarin sodium da ba shi da daidaito sosai, Na19⁻, yana tsayawa a 1.7 ko ƙasa da haka. A cikin giɓin, β tana faɗuwa zuwa kusan sifili: da babbar hanyar ta yi shiru, wata igiya mai rauni ƙwarai da yawanci take ɓoye, wadda take alamar siffar icosahedron, ta karɓi ragama.

Tagwaye mai molybdenum

Kwaikwayon ya nuna cewa irin wannan sokewa zai iya zama ruwan dare a tarin da ke kusan zagaye. Ƙungiyar ta gwada haka da Ag12Mo⁻, inda molybdenum ya maye gurbin tungsten da adadin electrons iri ɗaya. Kololuwa ɗaya mai kaifi kuma; giɓi kusan cikakke kuma, a kusan electronvolt 2.1 — sake, kusan electronvolt 0.87 sama da iyakar. Tun da ana iya daidaita girma da haɗin manyan zarra, marubutan suna ganin hanyar sarrafa fitar electron ta haske (photoemission) da gangan.

Caji da aka daidaita don ya dace

Ka’idar tana da iyakoki da marubutan suka bayyana. Orbital ɗin na daidai ya yi tsadar lissafi, don haka suka yi amfani da kimantawa. Wata igiya mai sauƙi da ke fita ba ta yi daidai da bayanan ba; maimakon haka, an tsara electron da ke tafiya kamar yana jin wani ɗan jan baya mai rauni daga tarin, caji mai tasiri (effective charge) na +0.37 na cajin asali (girman cajin electron, da alamar ƙari), wanda aka daidaita don ya dace da bayanan — hanyar da suke kira ta lura-da-gani (phenomenological). Kuma ba a iya ware Ag12Mo⁻ gaba ɗaya bisa nauyi daga tarin Ag13⁻ ba, don haka bakan haskensa (spectrum) yana da tsabta ne kawai har zuwa electronvolt 2.81.