Nā nīnau hoʻohālike e kūkākūkā ana i ka Beta (β) Decay
ʻO ka palaho radioactive ke kaʻina hana e hoʻokuʻu ai kahi nucleus atomic paʻa ʻole i nā ʻāpana e hoʻokō ai i kahi kūlana paʻa. Ma kēia ʻatikala, e kālele mākou i ka palaho beta (β), kahi ʻano palaho radioactive. ʻO kā mākou pahuhopu nui ka hoʻomaopopo ʻana i ka palaho beta ma o nā laʻana a me kā lākou mau hoʻonā. E hoʻomaka kākou ma ke aʻo ʻana i nā kumu o ka palaho beta ma mua o ka luʻu ʻana i nā laʻana.
Nā Kumu o ka Beta Decay
ʻO ka palaho beta e pili ana i ka hoʻololi ʻana o kekahi mau nuclei atomika ma ka hoʻokuʻu ʻana i nā ʻāpana beta. ʻElua ʻano o ka palaho beta:
1. Beta-minus (β-) decay: Ma kēia decay, loli kahi neutron i loko o ka nucleus i proton, kahi electron (i ʻike ʻia he beta particle), a me kahi electron antineutrino. ʻO ke kaulike hopena penei:
\[
n \rightarrow p + e^- + \bar{\nu}_e
\]
Maanei, he neutron ʻo \( n \), he proton ʻo \( p \), he electron (beta) ʻo \( e^- \), a he electron antineutrino ʻo \( \bar{\nu}_e \).
2. Beta-plus (β+) decay: Hana ʻia kēia ke loli kahi proton i loko o ka nucleus i neutron, positron (antielectron), a me kahi electron neutrino. ʻO ke kaulike:
\[
p \rightarrow n + e^+ + \nu_e
\]
Ma kahi ʻo \( e^+ \) he positron a ʻo \( \nu_e \) he electron neutrino.
Laʻana 1: Beta-minus Decay
Nīnau:
ʻO kahi nucleus carbon-14 (\( ^{14}_{6}\text{C} \)) e hele ana i ka palaho beta-minus. E hoʻoholo i nā huahana o kēia palaho a kākau i ka hoohalike nucleus.
Kūkākūkā:
ʻO ka mea mua, ʻike mākou he 6 ka helu atomika o ke kalapona-14 (\( ^{14}_{6}\text{C} \)) a he 14 ka helu nuipaʻa. I ka palaho beta-minus, hoʻololi kekahi o nā neutrons i loko o ka nucleus i proton. ʻO ke ʻano kēia, piʻi ka helu atomika o ka nucleus ma hoʻokahi anakahi, ʻoiai e mau ana ka helu nuipaʻa.
Eia ka hoʻohālikelike beta-minus decay no ke kalapona-14:
\[
^{14}_{6}\text{C} \rightarrow ^{14}_{7}\text{N} + e^- + \bar{\nu}_e
\]
Ma hea:
– ʻO ka huahana o ka palaho he naikokene-14 (\( ^{14}_{7}\text{N} \)).
– ʻO nā electrons (\( e^- \)) nā ʻāpana beta i hoʻokuʻu ʻia.
– ʻO \( \bar{\nu}_e \) he electron antineutrino i hoʻokuʻu ʻia hoʻi.
Laʻana 2: Beta-plus Decay
Nīnau:
ʻO ka nucleus fluorine-18 (\( ^{18}_{9}\text{F} \)) ke hele nei i ka palaho beta-plus. E hoʻoholo i nā huahana o kēia palaho a kākau i ka hoohalike nucleus.
Kūkākūkā:
ʻO ka helu atomika o Fluorine-18 (\( ^{18}_{9}\text{F} \)) he 9 a he helu nuipaʻa he 18. I ka palaho beta-plus, loli kahi proton i loko o ka nucleus i neutron e hoʻemi ana i ka helu atomika ma hoʻokahi, akā ua mau ka helu nuipaʻa.
Eia ka hoʻohālikelike beta-plus decay no ka fluorine-18:
\[
^{18}_{9}\text{F} \rightarrow ^{18}_{8}\text{O} + e^+ + \nu_e
\]
Ma hea:
– ʻO ka huahana o ka palaho he oxygen-18 (\( ^{18}_{8}\text{O} \)).
– He ʻāpana beta ka Positron (\( e^+ \)) i hoʻokuʻu ʻia.
– ʻO \( \nu_e \) kahi neutrino uila i hoʻokuʻu ʻia hoʻi.
Laʻana Nīnau 3: Ikehu Palaho
Nīnau:
E helu i ka ikehu i hoʻokuʻu ʻia i ka wā o ka palaho beta-minus inā palaho ka isotope strontium-90 (\( ^{90}_{38}\text{Sr} \)) i yttrium-90 (\( ^{90}_{39}\text{Y} \)). ʻO ke kaumaha o ka strontium-90 he 89,907738 u, a ʻo ke kaumaha o ka yttrium-90 he 89,907152 u. ʻO ke kaumaha o kahi electron he 0,000548 u.
Kūkākūkā:
Hiki ke helu ʻia ka ikehu i hoʻokuʻu ʻia i ka wā o ka beta-minus decay mai ka ʻokoʻa o ka nuipa ma waena o nā huahana a me nā reactants, a laila hoʻololi ʻia i ikehu me ka hoʻohana ʻana i ka hoohalike a Einstein \( E=mc^2 \).
ʻO ka loli o ka nuipa (\( \Delta m \)) ʻo ia ka ʻokoʻa ma waena o ka nuipa mua a me ka nuipa hope loa, me ka nuipa o ka electron i hoʻopuka ʻia:
\[
ʻO ka Delta m = (\text{mass } ^{90}_{38}\text{Sr}) – (\text{mass } ^{90}_{39}\text{Y} + \text{electron mass})
\]
Hoʻololi waiwai:
\[
ʻO ka Delta m = 89,907738 – (89,907152 + 0,000548)
\]
\[
ʻO ka Delta m = 0,000038
\]
Ke hoʻololi nei i nā loli nuipa i ka ikehu (1 u = 931.5 MeV/c²):
\[
E = \Delta m \times 931.5 \, \text{MeV/c}^2
\]
\[
E = 0,000038 \, \text{u} \times 931.5 \, \text{MeV}
\]
\[
E \approx 0,03537 \, \text{MeV}
\]
ʻO ka ikehu i hoʻokuʻu ʻia i ka wā o ka palaho ʻana ma kahi o 0,03537 MeV.
Ka hopena
He mea hoihoi ka palaho Beta e kōkua iā mākou e hoʻomaopopo i nā hoʻololi maalea e hiki ke hana i loko o nā nuclei atomika. Ma ke aʻo ʻana i ka palaho beta-minus a me beta-plus, hiki iā mākou ke ʻike pehea e hoʻololi ai nā mea i nā mea ʻē aʻe a helu i ka ikehu i hoʻokuʻu ʻia i ka wā o ke kaʻina hana. Ma o kēia pilikia hoʻohālike, loaʻa iā mākou kahi ʻike hohonu i loko o nā dinamika e pili ana i ka palaho radioactive a me ke koʻikoʻi o nā manaʻo kumu i ka physics nuklea.
