Ugunduzi wa Kwanza wa Oksijeni 28 na muundo wa kawaida wa ganda la muundo wa nyuklia   

Oksijeni-28 (²⁸O), the heaviest rare isotope of oxygen has been detected for the first time by Japanese researchers. Unexpectedly it was found to be short-lived and unstable despite meeting the “magic” number criteria of nyuklia utulivu.  

Oksijeni ina isotopu nyingi; zote zina protoni 8 (Z) kwenye viini vyake lakini hutofautiana kuhusiana na idadi ya neutroni (N). Isotopu imara ni ¹⁶O, ¹⁷O na ¹⁸O ambazo zina neutroni 8, 9 na 10 kwenye viini vyake mtawalia. Kati ya isotopu tatu thabiti, ¹⁶O ni nyingi zaidi ikijumuisha takriban 99.74% ya oksijeni yote inayopatikana katika maumbile. 

Iliyogunduliwa hivi majuzi ²⁸Isotopu ya O ina protoni 8 (Z=8) na neutroni 20 (N=20). Ilitarajiwa kuwa thabiti kwa sababu inakidhi mahitaji ya nambari ya "uchawi" kuhusiana na protoni na neutroni zote mbili (uchawi mara mbili) lakini ilipatikana kuwa ya muda mfupi na kuoza haraka.  

Ni nini hufanya kiini cha atomi kuwa thabiti? Je, ni kwa kiasi gani protoni na nyutroni zenye chaji chanya zimeshikiliwa pamoja kwenye kiini cha atomi?  

Under standard shell-model of nyuklia structure, protons and neutrons are thought to occupy shells. There is a limit on optimal number of nucleons (protons or nucleons) that can be accommodated a given “shell”. Nuclei are compact and more stable when “shells” are fully filled with a “specific numbers” of protons or neutrons. These “specific numbers” are called “magic” numbers.  

Hivi sasa, 2, 8, 20, 28, 50, 82, na 126 kwa ujumla huchukuliwa kuwa nambari za "uchawi". 

When both number of protons (Z) and number of neutrons (N) in a nucleus equal “magic” numbers, its considered to be a case of “doubly” magic which is associated with stable nyuklia structure. For example, ¹⁶O, isotopu iliyo thabiti zaidi na iliyo tele zaidi ya oksijeni ina Z=8 na N=8 ambazo ni nambari za "uchawi" na kesi ya uchawi maradufu. Vile vile, isotopu iliyogunduliwa hivi karibuni ²⁸O ina Z=8 na N=20 ambazo ni nambari za kichawi. Kwa hivyo, Oksijeni-28 ilitarajiwa kuwa dhabiti lakini imepatikana kuwa isiyo thabiti na ya muda mfupi katika jaribio (ingawa ugunduzi huu wa majaribio bado haujathibitishwa katika majaribio yanayorudiwa katika mipangilio mingine).  

Hapo awali, 32 ilipendekezwa kuwa nambari mpya ya uchawi ya nutroni lakini haikupatikana kuwa nambari ya uchawi katika isotopu za potasiamu. 

Standard shell-model of nyuklia structure, the current theory explaining how atomic nuclei are structured seem to insufficient at least in the case of ²⁸O isotopu.  

Nucleons (protoni na neutroni) zimeshikiliwa pamoja kwenye kiini kwa nguvu kali ya nyuklia. Uelewa wa uthabiti wa nyuklia na jinsi vipengee vinavyotengenezwa upo katika kukuza uelewa bora wa nguvu hii ya msingi.  

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Marejeo:  

1. Taasisi ya Teknolojia ya Tokyo. Habari za utafiti - Kuchunguza Nuclei Nutroni-Rich Nuclei: Uchunguzi wa Kwanza wa Oksijeni-28. Iliyochapishwa: Agosti 31, 2023. Inapatikana kwa https://www.titech.ac.jp/english/news/2023/067383  

2. Kondo, Y., Achouri, NL, Falou, HA et al. Uchunguzi wa kwanza wa ²⁸O. Nature 620, 965-970 (2023). https://doi.org/10.1038/s41586-023-06352-6 

3. Idara ya Nishati ya Marekani 2021. Habari - The Magic Is Gone kwa Neutron Number 32. Inapatikana kwa https://www.energy.gov/science/np/articles/magic-gone-neutron-number-32  

4. Koszorus, Á., Yang, XF, Jiang, WG et al. Chaji radii ya isotopu ya kigeni ya potasiamu changamoto nadharia ya nyuklia na tabia ya uchawi N = 32. Nat. Phys. 17, 439-443 (2021). https://doi.org/10.1038/s41567-020-01136-5 

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