========================================================================= Date: Mon, 3 Sep 2001 10:07:03 +1200 Reply-To: Radiocarbon Mailing List Sender: Radiocarbon Mailing List From: Rodger Sparks Subject: Re: Post-atomic contamination of C-14 samples Mime-Version: 1.0 Content-type: text/plain; charset="us-ascii" Sorry, I must continue to disagree. To see if absorption of a thermal neutron by 14N can lead to proton emission and 14C you can go to the atomic mass tables of (eg) Audi & Wapstra (1993) and do the maths. The precise numbers in the tables may have changed slightly over the years, but the conclusions remain the same. From the table of mass defects, expressed in keV, we have 14N 2863.419 14C 3019.894 1n 8071.323 1p 7288.969 ____________ ____________ 10934.742 10308.863 10943.742 - 10308.863 = 625.879 The 14N + n combination is heavier than 14C + p by +626 keV, which means that it is energetically advantageous for the absorption of a neutron to be followed by the emission of a proton. Since the Q value is positive it is not necessary to add any kinetic energy of the neutron to allow the reaction to proceed, so the reaction can take place with thermal neutrons. Of course, showing that a reaction can take place is not the same as showing that it will take place, or what the cross-section will be. For this we must be grateful to Mother Nature for fixing the values of the fundamental physical constants such that the 15N nucleus formed by adding a thermal neutron to 14N has a relatively high probability of decaying into 14C and a proton. When I first encountered this I was surprised that such a thing could happen, but that's how it is. Your argument that a thermal neutron does not have enough energy to allow the reaction fails because you must consider -all- masses and energies involved, including the neutron and proton. Physically, what occurs can be thought of as a neutron "falling" into the potential well of the 14N nucleus as it makes a random close encounter. The potential energy released in the process appears as excitation energy of the compound 15N nucleus, and eventually a sufficiently large portion gets concentrated in one of the outer protons to allow it to escape. (That explanation would probably fail me in a nuclear physics exam, but it gives a simple picture that is not too far from reality). The 13C + n reaction is a bit of a red herring. It does occur, but for thermal neutrons the cross-section is of the order of a milli-barn, compared with 1.8 barns for the 14N + n reaction, and you basically say the same thing. There are resonances for higher energy neutrons, but the cross-section does not really compete with 14N + n. The 14N + thermal neutron reaction is important because, if nitrogen is present, it will dominate 14C production. Although nuclear explosions and cosmic ray interactions produce fast neutrons, those neutrons are rapidly thermalised in the atmosphere and the ground. The opportunities for fast neutron production of 14C are relatively limited. In the particular conditions of, say, a reactor core (eg Chernobyl) the situation can be quite different, but that is not what we are considering here. Rodger Sparks ref. G Audi, A.H. Wapstra Nuclear Physics A565 (1993) >My intended point was more about the energy of the neutrons that cause >the reaction and the meaning of "thermal" in describing the energy of >the neutrons. The mass defect between the N and C nuclides corresponds >to a threshold energy of 149 keV. Completely thermalized neutrons have >an average energy that is only a small fraction of an eV, not enough to >make the reaction possible. > >However, the fine print on a table that confirms your cross section of >1.83 barns, says that for practical purposes they include as "thermal" >neutrons, any that have an energy up to 500 keV, more than enough to >make the reaction go. So it depends on which "practical" considerations >are behind the terminology. =========================================================================== To unsubscribe from this list, send the command SIGNOFF C14-L to LISTSERV@LISTSERV.ARIZONA.EDU, or send a request to C14-L-request@LISTSERV.ARIZONA.EDU. ========================================================================= Date: Tue, 4 Sep 2001 16:36:53 -0500 Reply-To: Radiocarbon Mailing List Sender: Radiocarbon Mailing List From: Chuck Blatchley Organization: Pittsburg State University Subject: Re: Post-atomic contamination of C-14 samples MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Rodger Sparks, Thank you kindly for straightening me out. It's been a while since I played with Q values. Chuck Blatchley =========================================================================== To unsubscribe from this list, send the command SIGNOFF C14-L to LISTSERV@LISTSERV.ARIZONA.EDU, or send a request to C14-L-request@LISTSERV.ARIZONA.EDU. ========================================================================= Date: Thu, 13 Sep 2001 19:18:19 +0300 Reply-To: yfacorellis@ims.demokritos.gr Sender: Radiocarbon Mailing List From: Yorgos Facorellis Subject: Re: C14 and Archaeology - First Circular In-Reply-To: Mime-Version: 1.0 Content-Type: multipart/alternative; boundary="=====_100039789929358=_" --=====_100039789929358=_ Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable Dear Colleague, I am interested to participate to the 4th 14C and Archaeology Symposium.= When is it planned to send us the 2nd circular? Best regards, Dr Yorgos Facorellis Laboratory of Archaeometry Institute of Materials Science NCSR "Demokritos" 153 10 Agia Paraskevi Attikis Greece *********** REPLY SEPARATOR *********** On 1/5/2001 at 1:02 =EC=EC Tom Higham wrote: 14C AND ARCHAEOLOGY FOURTH SYMPOSIUM APRIL 9-13, 2002 OXFORD Dear Colleagues, We are pleased to announce the dates and venue for the Fourth 14C and= Archaeology Symposium, which will be held in Oxford between April 9-13,= 2002. The conference is being organised by the Oxford Radiocarbon Accelerator= Unit, Research Lab for Archaeology and the History of Art, University of= Oxford. We invite you to register an offer of interest in attending the conference= by sending an email to orau@archaeology-research.oxford.ac.uk You will= then be put on an email address list for the second circular. The following sessions are proposed, but we do invite suggestions for= additional, or perhaps replacement sessions from interested participants: 1. Colonisations and extinctions. 2. High resolution dating. 3. Problems commonly encountered. 4. World archaeology. 5. European archaeology. Organising Committee: Prof. R. Hedges, Dr C. Ramsey, Dr T. Higham, Mrs C. Owen. Address for correspondence: Oxford Radiocarbon Accelerator Unit, Research Laboratory for Archaeology and the History of Art, 6 Keble Road, Oxford OX1 3QJ, England. Fax: + 44 0 1865 273932 Email: orau@archaeology-research.oxford.ac.uk -- Dr Tom Higham, Oxford Radiocarbon Accelerator Unit, Research Laboratory for Archaeology and the History of Art, 6 Keble Road, Oxford OX1 3QJ, England. WEBinfo: http://www.c14dating.com --=====_100039789929358=_ Content-Type: text/html; charset="us-ascii" C14 and Archaeology - First Circular
Dear Colleague,
 
I am interested to participate to the 4th 14C and Archaeology Symposium. When is it planned to send us the 2nd circular?
 
Best regards,
 
Dr Yorgos Facorellis
Laboratory of Archaeometry
Institute of Materials Science
NCSR "Demokritos"
153 10 Agia Paraskevi Attikis Greece

*********** REPLY SEPARATOR ***********

On 1/5/2001 at 1:02 ìì Tom Higham wrote:
14C AND ARCHAEOLOGY
FOURTH SYMPOSIUM

APRIL 9-13, 2002

OXFORD


Dear Colleagues,

We are pleased to announce the dates and venue for the Fourth 14C and Archaeology Symposium, which will be held in Oxford between April 9-13, 2002.

The conference is being organised by the Oxford Radiocarbon Accelerator Unit, Research Lab for Archaeology and the History of Art, University of Oxford.
We invite you to register an offer of interest in attending the conference by sending an email to orau@archaeology-research.oxford.ac.uk  You will then be put on an email address list for the second circular.

The following sessions are proposed, but we do invite suggestions for additional, or perhaps replacement sessions from interested participants:
1. Colonisations and extinctions.
2. High resolution dating.
3. Problems commonly encountered.
4. World archaeology.
5. European archaeology.


Organising Committee:
Prof. R. Hedges, Dr C. Ramsey, Dr T. Higham, Mrs C. Owen.

Address for correspondence:

Oxford Radiocarbon Accelerator Unit,
Research Laboratory for Archaeology and the History of Art,
6 Keble Road,
Oxford OX1 3QJ,
England.
Fax: + 44 0 1865 273932
Email: orau@archaeology-research.oxford.ac.uk
--
Dr Tom Higham,
Oxford Radiocarbon Accelerator Unit,
Research Laboratory for Archaeology and the History of Art,
6 Keble Road,
Oxford OX1 3QJ,
England.
WEBinfo: http://www.c14dating.com
--=====_100039789929358=_-- =========================================================================== To unsubscribe from this list, send the command SIGNOFF C14-L to LISTSERV@LISTSERV.ARIZONA.EDU, or send a request to C14-L-request@LISTSERV.ARIZONA.EDU. ========================================================================= Date: Fri, 14 Sep 2001 09:29:12 +1200 Reply-To: Radiocarbon Mailing List Sender: Radiocarbon Mailing List From: Tom Higham Subject: C14 and Archaeology conference Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" ; format="flowed" The second circular for the C14 and Archaeology conference will be sent very shortly. We are currently finalising registration costs and within the next fortnight this information will be mailed to first circular registrants and placed on a web page. Sincerely, Tom Higham, ORAU -- Dr Tom Higham, Oxford Radiocarbon Accelerator Unit, Research Laboratory for Archaeology and the History of Art, 6 Keble Road, University of Oxford, Oxford OX1 3QJ, England. ORAU Web page: http://rlaha.ox.ac.uk/orau WEBinfo: http://www.c14dating.com =========================================================================== To unsubscribe from this list, send the command SIGNOFF C14-L to LISTSERV@LISTSERV.ARIZONA.EDU, or send a request to C14-L-request@LISTSERV.ARIZONA.EDU. ========================================================================= Date: Sat, 15 Sep 2001 10:14:59 +0300 Reply-To: yfacorellis@ims.demokritos.gr Sender: Radiocarbon Mailing List From: Yorgos Subject: Re: C14 and Archaeology conference MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Many thanks for the information. Regards, Yorgos Facorellis ----- Original Message ----- From: Tom Higham To: Sent: Friday, September 14, 2001 12:29 AM Subject: C14 and Archaeology conference > The second circular for the C14 and Archaeology conference will be > sent very shortly. We are currently finalising registration costs and > within the next fortnight this information will be mailed to first > circular registrants and placed on a web page. > Sincerely, > Tom Higham, > ORAU > > -- > Dr Tom Higham, > Oxford Radiocarbon Accelerator Unit, > Research Laboratory for Archaeology and the History of Art, > 6 Keble Road, > University of Oxford, > Oxford OX1 3QJ, > England. > ORAU Web page: http://rlaha.ox.ac.uk/orau > WEBinfo: http://www.c14dating.com > > =========================================================================== > To unsubscribe from this list, send the command SIGNOFF C14-L to > LISTSERV@LISTSERV.ARIZONA.EDU, or send a request to C14-L-request@LISTSERV.ARIZONA.EDU. > =========================================================================== To unsubscribe from this list, send the command SIGNOFF C14-L to LISTSERV@LISTSERV.ARIZONA.EDU, or send a request to C14-L-request@LISTSERV.ARIZONA.EDU. ========================================================================= Date: Thu, 27 Sep 2001 16:32:00 EDT Reply-To: Radiocarbon Mailing List Sender: Radiocarbon Mailing List From: Ernie Rogers Subject: Need advice on C14 dating MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="part1_7b.1bccb68d.28e4e6c0_boundary" --part1_7b.1bccb68d.28e4e6c0_boundary Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit To list members: I have a problem on which I hope to get some advice. I have an aunt and uncle that are well on in years (87 and 94). My aunt told me a story about her father in the 1940s, that a woman he had befriended entrusted him with an ancient relic. It was a set of wooden beads, said to be 2000 years old, and having historic significance. My aunt is nearing the end of her life and is trying to decide what to do with these beads. When I visited her a few months ago, she got a pair of scissors and cut the string of the necklace, and gave me one of the beads. She said that since I am a physicist, she would like me to verify how old the beads are, and that she would like to find a museum that might like to have them. My aunt and uncle have put me in a tough spot because I just don't have the money to pay the usual fee for the analysis (nor do they). Some advice would be appreciated. Since this discussion may not be of general interest, replies may be sent directly to me as appropriate. (The bead I have is spherical, about 2 cm. diameter, and appears to be painted with a shiny black lacquer.) Ernest Rogers Pleasant Grove, Utah --part1_7b.1bccb68d.28e4e6c0_boundary Content-Type: text/html; charset="US-ASCII" Content-Transfer-Encoding: 7bit To list members:

I have a problem on which I hope to get some advice.  I have an aunt and uncle that are well on in years (87 and 94).  My aunt told me a story about her father in the 1940s, that a woman he had befriended entrusted him with an ancient relic.  It was a set of wooden beads, said to be 2000 years old, and having historic significance.  My aunt is nearing the end of her life and is trying to decide what to do with these beads.  When I visited her a few months ago, she got a pair of scissors and cut the string of the necklace, and gave me one of the beads.  She said that since I am a physicist, she would like me to verify how old the beads are, and that she would like to find a museum that might like to have them.

My aunt and uncle have put me in a tough spot because I just don't have the money to pay the usual fee for the analysis (nor do they).  Some advice would be appreciated.  Since this discussion may not be of general interest, replies may be sent directly to me as appropriate.

(The bead I have is spherical, about 2 cm. diameter, and appears to be painted with a shiny black lacquer.)

Ernest Rogers
Pleasant Grove, Utah
--part1_7b.1bccb68d.28e4e6c0_boundary-- =========================================================================== To unsubscribe from this list, send the command SIGNOFF C14-L to LISTSERV@LISTSERV.ARIZONA.EDU, or send a request to C14-L-request@LISTSERV.ARIZONA.EDU. ========================================================================= Date: Fri, 28 Sep 2001 11:32:07 +0100 Reply-To: Radiocarbon Mailing List Sender: Radiocarbon Mailing List From: Caitlin Buck Organization: University of Sheffield Subject: Relaunch of BCal MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Dear All Just to let you know that I have recently moved jobs (from Cardiff to Sheffield). As a result, BCal has a new URL. We will be happy to welcome new users and old friends alike at: http://bcal.shef.ac.uk/ For those of you who haven't used the software before, it is on-line Bayesian radiocarbon calibration software which is offered free of charge to all researchers and academic staff and students around the world. If you operate a commercial service, we would also be happy for you to make use of the service, but we will ask for a small charge - please ask me about charges. Do let me know if you have any problems at all getting onto the new service and I will do what I can to help. Caitlin -- Dr Caitlin Buck Email: c.e.buck@sheffield.ac.uk Dept of Probability and Statistics University of Sheffield Tel: +44 114 222 3715 (direct) Hicks Building Tel: +44 114 222 3751 (secretary) Hounsfield Road Fax: +44 114 222 3759 Sheffield S3 7RH =========================================================================== To unsubscribe from this list, send the command SIGNOFF C14-L to LISTSERV@LISTSERV.ARIZONA.EDU, or send a request to C14-L-request@LISTSERV.ARIZONA.EDU.