Te Pirau o te Ārapa (α)
Ko te pirau ārepa (α) tētahi o ngā momo matua e toru o te pirau irahiko, tae atu ki te pirau beta (β) me te pirau gamma (γ). He mea tino nui tēnei āhuatanga i roto i te ahupūngao karihi me te pūtaiao rauemi, ā, he pānga mahi anō hoki ki ngā mara o te rongoā karihi, te mana karihi, me te taiao.
Te Mārama ki te Pirau Ārapa
Ko te pirau ārepa te tukanga e tukuna ai e te karihi ngota kore pumau he matūriki ārepa hei whakatutuki i tētahi whirihoranga pumau ake. Ko ngā matūriki ārepa he rua ngā porotana me rua ngā iōnitā, he rite tonu ki te karihi o te ngota helium-4 (He-4). Ina pāngia te karihi ngota e te pirau ārepa, ka ngaro ngā porotana e rua me ngā iōnitā e rua, ka hua ake he karihi ngota hou he iti ake te tau ngota me te papatipu ngota iti iho.
Ka taea te tuhi i te whārite tauhohenga taketake mō te pirau ārepa penei:
\[ _Z^AX \rightarrow _{Z-2}^{A-4} Y + \alpha \]
kāore i te mana:
– Ko te \( _Z^AX \) te karihi ngota i mua i te pirau me te tau papatipu \( A \) me te tau ngota \( Z \),
– Ko te pūtake o te pirau ko \( _{Z-2}^{A-4} Y \)
– He matūriki ārepa a \( \alpha \).
Hei tauira, ka pirau te ūranium-238 (\( _{92}^{238} U \)) ki te Thorium-234 (\( _{90}^{234} Th \)):
\[ _{92}^{238} U \rightarrow _{90}^{234} Th + \alpha \]
Tikanga Pirau Ārepa
Ka puta te pirau ārepa nā te kaha karihi e mahi ana i roto i te karihi. Kei roto i te karihi ngota ngā porotana me ngā niutorone e puritia ana e te kaha kaha. Ahakoa te kaha hiko i waenga i ngā porotana kua utua pai ka panaia rātou kia wehe, he kaha te kaha kaha ki te pupuri i a rātou kia noho tahi i te nuinga o te wā. Heoi, i roto i ngā karihi taumaha he maha ngā porotana, ka nui rawa te pana hikohiko ka kore e pumau te karihi.
Mō ngā karihi taumaha, he tino whai hua te tukunga o ngā matūriki ārepa ki te whakaheke i te pūngao o te pūnaha. He matūriki pumau ngā matūriki ārepa, he nui te pūngao here mō ia karihiona, nō reira ka āwhina tā rātou tukunga i te karihi kia nui ake te pumau.
Ngā Āhuatanga o ngā Matūriki Āra
He maha ngā āhuatanga nui o ngā matūriki ārepa e whakaata ana i ō rātou āhuatanga ā-tinana me ngā taunekeneke ki te matū:
1. Papatipu me te Utu: Ko te papatipu o ia matūriki ārepa he tata ki te 4 ngā waeine papatipu ngota (u) me te utu he +2 e, nā te mea e rua ngā porotana me ngā iōnitā e rua.
2. Pūngao me te Tere: He tino teitei te pūngao nekeneke o ngā matūriki ārepa (he maha ngā MeV te nuinga) engari he iti noa iho te tere ki te whakatauritea ki ngā matūriki beta, ki ngā hihi gamma rānei.
3. Te Wāhi Whakauru me te Awhe: Nā te mea he nui te utu me te papatipu o ngā matūriki ārepa, he poto noa iho te awhe i roto i te matū. Ka taea te aukati ngāwari mā te torutoru henimita o te hau, mā te torutoru maikiromita rānei o te rauemi matotoru pērā i te pepa, i te kiri tangata rānei.
4. Te whaka-ioniti: He tino whaka-ioniti ngā matūriki ārepa, arā, ka nui te whaka-ioniti i roto i te rauemi e tika ana mā rātou. Nā tēnei ka tino whai hua rātou ki te whakaatu i te kiriata whakaahua, ki te tuhi rānei i ngā kanapa i roto i ngā taputapu kite.
Taupānga Pirau Āra
1. Rongoā karihi: E whakamahia ana ngā pūtake irahiko ārepa i roto i ētahi maimoatanga hauora, inā koa i roto i te rongoā i te mate pukupuku. Hei tauira, e whakamahia ana te radium-223 hei rongoā i ngā wheua kua horapa ki roto.
2. Ngā Pūoko Auahi: He maha ngā pūoko auahi o te whare e whakamahi ana i te americium-241, he pūoko alpha, hei kimi i te auahi. Ka whakakorikori ngā matūriki alpha e tukuna ana i te hau i roto i te rūma kimi; ina uru te auahi ki roto i tēnei rūma, ka rerekē te kawe hiko, ka puta te whakaoho.
3. Te Whakatau Ine Irirangi: Mā ngā tikanga whakatau ine irirangi pērā i te whakatau ine i te uranium-lead ka whakamahia te pirau ārepa o te uranium me ngā isotopes thorium hei whakatau i te pakeke o ngā toka me ngā kohuke.
4. Te Haumarutanga me te Hiranga o te Ope Taua: Nā te iti o te urunga o ngā matūriki ārepa, kāore ngā rauemi e tuku ārepa e tino whakararuraru ana i te irahiko o waho, ā, ka taea te whakahaere haumaru me te tiaki noa; heoi, ina manawahia, ina horomia rānei, ka tino morearea.
Ngā Pānga me ngā Tūponotanga o te Pirau Ārapa
Ahakoa kāore ngā matūriki alpha e tino uru ki roto, ka tino morearea pea mēnā ka hongia, ka horomia rānei ngā rauemi irahiko e tuku ana i ngā matūriki alpha. I ēnei wā, ka taea e te irahiko alpha te whakararuraru i ngā kiko ora mā te ionization tika. Nō reira, me tino tupato i te wā e whakahaere ana, e penapena ana hoki i ngā rauemi e tuku ana i te alpha, me te whai i ngā aratohu haumaru irahiko tino pakari.
Ngā Rangahau me ngā Rangahau mō te Pirau Āra
Nā te rangahau i te pirau ārepa kua homai he māramatanga nui ki te āhua taketake o ngā taunekeneke karihi me te karihi. I whakamāramahia tuatahitia te ariā o te pirau ārepa e George Gamow i te tau 1928 mā te whakamahi i te tikanga o te whakatō irahiko, he āhuatanga e taea ai e ngā matūriki te uru ki ngā arai pea e kore e taea e ai ki te ahupūngao matarohia.
E ai ki tēnei ariā, ko ngā matūriki ārepa i roto i te karihi e kiia ana he pūnaha e whakataetae ana ki tētahi ārai pea e karapoti ana i te karihi. Ahakoa kāore i a rātou te kaha nekeneke e ranea ana hei whiti i roto i te ārai i te tikanga matarohia, ko te tūponotanga ka taea e rātou te 'wero' i te ārai mā te poka irahiko ka taea te pirau. Mā ēnei tātaitanga ka puta he matapae mō te haurua-ora me te kaha o ngā matūriki ārepa e rite ana ki ngā kitenga whakamātautau.
Whakamutunga
He āhuatanga taketake te pirau ā-ira i roto i te ahupūngao karihi, e pā ana ki te tukunga o ngā matūriki ā-ira (e rua ngā porotona me e rua ngā iōnitā) mai i ngā karihi ngota kore pumau. Ehara i te mea he mea nui noa iho tēnei tukanga mō te māramatanga taketake ki te āhua o ngā karihi ngota, engari he nui hoki ngā tono mahi i roto i te hangarau hauora, ahumahi, me te pūtaiao.
Ahakoa he iti te urunga o te irahiko alpha, ā, he ngāwari noa iho te aukati, me tino tupato te whakahaere i ngā rauemi e tuku ana i te irahiko alpha kia kore ai e pāngia ngā kiko koiora e te pānga o roto. Kei te haere tonu ngā rangahau hōhonu mō te pirau alpha ki te whakarato i ngā māramatanga hou ki te ahupūngao karihi, ā, ka hua ake he tono hangarau haumaru ake, whai hua ake hoki i roto i te whānuitanga o ngā mara.
