From owner-chemistry@ccl.net Fri Nov 30 03:23:01 2007 From: "feng zhu zhufengcc|,|gmail.com" To: CCL Subject: CCL: spin changes through the reaction Message-Id: <-35737-071130031526-23739-5ntI5CsinuADGjqzj/Ti/Q]_[server.ccl.net> X-Original-From: "feng zhu" Content-Type: multipart/alternative; boundary="----=_Part_974_23728209.1196410514067" Date: Fri, 30 Nov 2007 16:15:14 +0800 MIME-Version: 1.0 Sent to CCL by: "feng zhu" [zhufengcc-,-gmail.com] ------=_Part_974_23728209.1196410514067 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Content-Disposition: inline Thank you for you reply! I my mind, if singlet A and triplet B are the most stable states, then there must be a spin change during the reaction if the reaction can happen. So there should be three possibililities: (1) singlet A-->triplet A --> triplet B, (2) singlet A-->singlet B--> triplet B, (3) singlet A-->singlet C--> triplet C --> triplet B, Do you agree? "But as far as I know, the reaction from singlet A to triplet B is a spin-forbidden process." -- then how we study the reaction O2+C -->CO2 ? Best regards, Zhu 2007/11/29, d w : > > > hi, zhu, > > you may consider the reaction in this way: > > 1. the reaction proceeds on the surface of spin=1 as singlet is the most > stable state of A; this produces singlet B; > 2. a crossing (or avoided crossing) (CI) may exist between the surfaces of > singlet and triplet of B from which the singlet B will relax to triplet B. > > of course, in principle there is another possibility that the excitation > of singlet A to triplet happens first, followed by the reaction from A to B. > therefore, you need analyze your system to see if one is superior over > another one, or they compete each other. But as far as I know, the reaction > from singlet A to triplet B is a spin-forbidden process. > > good luck. > > best, > dongqi wang > > ---------------------------------------- > > From: owner-chemistry ~ ccl.net > > To: wangdq2100 ~ hotmail.com > > Subject: CCL: spin changes through the reaction > > Date: Wed, 28 Nov 2007 05:30:51 -0500 > > > > > > Sent to CCL by: "feng zhu" [zhufengcc * gmail.com] > > Dear All, > > > > I want to know how to deal with the spin-cross in the reaction path. > > > > For example, a reaction from A to B: > > For A, spin=1 is the most stable state while spin=3 is excited state. > > But for B, spin=3 is the most stable state and spin=1 is excited state. > > > > Then how we calculate this reaction path, how we define the barriar of > this reaction, and how we estimate the possibility of this reaction? > > > > Thank you very much! > > > > Zhu> > > > Search Messages: http://www.ccl.net/htdig (login: ccl, Password: > search)> > > > -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ > > > > > > > > > _________________________________________________________________ > Connect and share in new ways with Windows Live. > > http://www.windowslive.com/connect.html?ocid=TXT_TAGLM_Wave2_newways_112007 -- ------------------ Zhu feng Department of Physics, Anhui University, Hefei, China -- ------------------ Zhu feng Department of Physics, Anhui University, Hefei, China ------=_Part_974_23728209.1196410514067 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Content-Disposition: inline
Thank you for you reply!
 
I my mind, if singlet A and triplet B are the most stable states, then there must be a spin change during the reaction if the reaction can happen.
So there should be three possibililities:
(1) singlet A-->triplet A --> triplet B,
(2) singlet A-->singlet B--> triplet B,
(3) singlet A-->singlet C--> triplet C --> triplet B,
 
Do you agree?
 
"But as far as I know, the reaction from singlet A to triplet B is a spin-forbidden process." 
-- then how we study the reaction O2+C -->CO2 ?
 
Best regards,
Zhu


 
2007/11/29, d w <wangdq2100 ~ hotmail.com>:

hi, zhu,

you may consider the reaction in this way:

1. the reaction proceeds on the surface of spin=1 as singlet is the most stable state of A; this produces singlet B;
2. a crossing (or avoided crossing) (CI) may exist between the surfaces of singlet and triplet of B from which the singlet B will relax to triplet B.

of course, in principle there is another possibility that the excitation of singlet A to triplet happens first, followed by the reaction from A to B. therefore, you need analyze your system to see if one is superior over another one, or they compete each other. But as far as I know, the reaction from singlet A to triplet B is a spin-forbidden process.

good luck.

best,
dongqi wang

----------------------------------------
> From: owner-chemistry ~ ccl.net
> To: wangdq2100 ~ hotmail.com
> Subject: CCL: spin changes through the reaction
> Date: Wed, 28 Nov 2007 05:30:51 -0500
>
>
> Sent to CCL by: "feng  zhu" [zhufengcc * gmail.com]
> Dear All,
>
> I want to know how to deal with the spin-cross in the reaction path.
>
> For example, a reaction from A to B:
> For A, spin=1 is the most stable state while spin=3 is excited state.
> But for B, spin=3 is the most stable state and spin=1 is excited state.
>
> Then how we calculate this reaction path, how we define the barriar of this reaction, and how we estimate the possibility of this reaction?
>
> Thank you very much!
>
> Zhu
>
>
>
>
>
>
>
>
> E-mail to subscribers: CHEMISTRY ~ ccl.net or use:
>       http://www.ccl.net/cgi-bin/ccl/send_ccl_message
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>

_________________________________________________________________
Connect and share in new ways with Windows Live.
http://www.windowslive.com/connect.html?ocid=TXT_TAGLM_Wave2_newways_112007



--
------------------
Zhu feng
Department of Physics,
Anhui University, Hefei, China

--
------------------
Zhu feng
Department of Physics,
Anhui University, Hefei, China ------=_Part_974_23728209.1196410514067-- From owner-chemistry@ccl.net Fri Nov 30 05:55:00 2007 From: "feng zhu zhufengcc*gmail.com" To: CCL Subject: CCL: spin changes through the reaction Message-Id: <-35738-071130034128-1340-N7CdpzYbA2BowA1QP3ZusQ||server.ccl.net> X-Original-From: "feng zhu" Content-Type: multipart/alternative; boundary="----=_Part_914_19601892.1196408290253" Date: Fri, 30 Nov 2007 15:38:10 +0800 MIME-Version: 1.0 Sent to CCL by: "feng zhu" [zhufengcc++gmail.com] ------=_Part_914_19601892.1196408290253 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Content-Disposition: inline Thank you for you reply! For example, in a reaction, spin=1 A-->TS1-->B, spin=3 A'-->TS3-->B' If we can find the the corssing point is C. It is clear that the energy of C is always below the energy of TS1 and TS2, unless C=TS1 or C=TS2. Then which one will give the barriar? TS1/TS2, or C ? --If we don't take account of spin-forbidden, I think it should be C. Am I right? Now the question is how to "identify the crossing of the two potential energy surfaces to locate the activation barrier". C is in both paths ( A-->B and A'-->B') with the same structure but different spin. Could you give me some suggestion on how to find C point? Best regards, Zhu 2007/11/29, nokophala[#]aim.com : > > You could calculate the reaction profile for each spin state, then > identify the crossing of the two potential energy surfaces to locate the > activation barrier. But a parameter that will remain unknown is the spin > changing probability. Sometimes, even if activation energy is low, spin > crossing can be difficult; These types of reactions are said to be spin > forbidden. > -----Original Message----- > > From: feng zhu zhufengcc{:}gmail.com > To: Phala, Noko > Sent: Wed, 28 Nov 2007 4:30 am > Subject: CCL: spin changes through the reaction > > > Sent to CCL by: "feng zhu" [zhufengcc * gmail.com] > Dear All, > > I want to know how to deal with the spin-cross in the reaction path. > > For example, a reaction from A to B: > For A, spin=1 is the most stable state while spin=3 is excited state. > But for B, spin=3 is the most stable state and spin=1 is excited state. > > Then how we calculate this reaction path, how we define the barriar of this > reaction, and how we estimate the possibility of this reaction? > > Thank you very much! > > ZhuE-mail to subscribers: CHEMISTRY-$-ccl.net or use:> > E-mail to administrators: CHEMISTRY-REQUEST-$-ccl.net or usehttp://www.ccl.net/chemistry/sub_unsub.shtml > ------------------------------ > More new features than ever. Check out the new AIM(R) Mail > ! > > -- ------------------ Zhu feng Department of Physics, Anhui University, Hefei, China ------=_Part_914_19601892.1196408290253 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Content-Disposition: inline
 
Thank you for you reply!
 
For example, in a reaction,
spin=1 A-->TS1-->B,
spin=3 A'-->TS3-->B'
If we can find the the corssing point is C.
It is clear that the energy of C is always below the energy of TS1 and TS2, unless C=TS1 or C=TS2.
Then which one will give the barriar? TS1/TS2, or C ? --If we don't take account of spin-forbidden, I think it should be C. Am I right?
 
Now the question is how to "identify the crossing of the two potential energy surfaces to locate the activation barrier".
 
C is in both paths ( A-->B and A'-->B') with the same structure but different spin. Could you give me some suggestion on how to find C point?
 
Best regards,
Zhu
 
 
 
 


 
2007/11/29, nokophala[#]aim.com <owner-chemistry!A!ccl.net>:
You could calculate the reaction profile for each spin state, then identify the crossing of the two potential energy surfaces to locate the activation barrier. But a parameter that will remain unknown is the spin changing probability. Sometimes, even if activation energy is low, spin crossing can be difficult; These types of reactions are said to be spin forbidden.
-----Original Message-----
> From: feng zhu zhufengcc{:}gmail.com <owner-chemistry-$-ccl.net>
To: Phala, Noko <nokophala-$- aim.com>
Sent: Wed, 28 Nov 2007 4:30 am
Subject: CCL: spin changes through the reaction


Sent to CCL by: "feng  zhu" [zhufengcc * gmail.com]
Dear All,

I want to know how to deal with the spin-cross in the reaction path.

For example, a reaction from A to B:
For A, spin=1 is the most stable state while spin=3 is excited state.
But for B, spin=3 is the most stable state and spin=1 is excited state.

Then how we calculate this reaction path, how we define the barriar of this 
reaction, and how we estimate the possibility of this reaction?

Thank you very much!

ZhuE-mail to subscribers: CHEMISTRY-$-ccl.net or use:
      http://www.ccl.net/cgi-bin/ccl/send_ccl_message

E-mail to administrators: CHEMISTRY-REQUEST-$-ccl.net or use
      http://www.ccl.net/cgi-bin/ccl/send_ccl_messagehttp://www.ccl.net/chemistry/sub_unsub.shtml


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More new features than ever. Check out the new AIM(R) Mail!
 



--
------------------
Zhu feng
Department of Physics,
Anhui University, Hefei, China ------=_Part_914_19601892.1196408290253-- From owner-chemistry@ccl.net Fri Nov 30 09:17:01 2007 From: "Conley, Michael mconley^^leadscope.com" To: CCL Subject: CCL: FDA Marketed Drugs Database Now Available Message-Id: <-35739-071130083108-14892-i0w3KkeuTUPZQ3XzF8ERow__server.ccl.net> X-Original-From: "Conley, Michael" Content-class: urn:content-classes:message Content-Type: multipart/alternative; boundary="----_=_NextPart_001_01C83350.B935D25F" Date: Fri, 30 Nov 2007 07:58:37 -0500 MIME-Version: 1.0 Sent to CCL by: "Conley, Michael" [mconley/./leadscope.com] This is a multi-part message in MIME format. ------_=_NextPart_001_01C83350.B935D25F Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable Leadscope Announces the Availability of two FDA Databases (Marketed Drugs & Acute Toxicity) =20 Columbus, Ohio November 30, 2007 - Leadscope announces the availability of two new FDA Databases. These databases have been created using non-proprietary data from the FDA files through a Cooperative Research & Development Agreement (CRADA) between the U. S. Food & Drug Administration and Leadscope, Inc. The new databases are: =20 FDA CDER 2007 Marketed Drugs Database FDA CFSAN 2007 Acute Toxicity Database =20 The annual license fee for an organization wide license is $250 per database. =20 The FDA CDER Marketed Drugs database contains information on 5,813 drug compounds. Data records have been accumulated form the following sources: * Drugs ]=[ FDA 1,931 compounds * FDA Orange Book 1,851 compounds * National Drug Code Directory 1,346 compounds * NLM Medical Subject Heading 5,418 compounds The FDA CFSAN 2007 Acute Toxicity database contains information on approximately 1,071 direct food additives covering 1,636 tests.=20 * Test system includes=20 * rats: 950 chemicals=20 * mice: 366 chemicals=20 * Compound-level LD50 values recorded in FDA CFSAN PAFA database To view a pre-recorded demonstration of the databases visit www.leadscope.com/demos. For more information or to license the FDA Databases, please visit Leadscope's website at www.leadscope.com/products.=20 =20 If you have excess budget funds remaining as 2007 comes to an end, consider using those excess funds to license the FDA databases. If you have any questions regarding the databases, please contact Leadscope at info]=[leadscope.com. =20 =20 Mike Conley =20 =20 ************************************** Michael Conley Leadscope, Inc. 1393 Dublin Road Columbus, Ohio 43215 614-675-3732 fax mconley]=[leadscope.com=20 =20 ------_=_NextPart_001_01C83350.B935D25F Content-Type: text/html; charset="us-ascii" Content-Transfer-Encoding: quoted-printable

Leadscope Announces the = Availability of two FDA Databases (Marketed Drugs & Acute = Toxicity)

 

Columbus, Ohio November 30, 2007 –  = Leadscope announces the availability of two new FDA Databases.   These databases have been created using non-proprietary data from the FDA = files through a Cooperative Research & Development Agreement (CRADA) = between the U. S. Food & Drug Administration and Leadscope, Inc.  The new databases are:

 

FDA CDER 2007 Marketed Drugs Database

FDA CFSAN 2007 Acute Toxicity Database

 

The annual license fee for an organization wide license is = $250 per database.

 

The FDA CDER Marketed Drugs database contains information = on 5,813 drug compounds.  Data records have been accumulated form the = following sources:

  • Drugs ]=[ FDA 1,931 = compounds
  • FDA Orange = Book       1,851 compounds
  • National Drug Code Directory  1,346 compounds
  • NLM Medical Subject Heading =            5,418 compounds

The FDA CFSAN 2007 Acute Toxicity = database contains information on approximately 1,071 direct food = additives covering 1,636 tests.

  • Test system includes
    • rats: 950 chemicals
    • mice: 366 chemicals
  • Compound-level LD50 values recorded in = FDA CFSAN PAFA database

To view a pre-recorded demonstration of the databases visit = www.leadscope.com/demos.  For more information or = to license the FDA Databases, please visit Leadscope’s website = at www.leadscope.com/products= .

 

If you have excess budget funds remaining as 2007 comes to an end, consider = using those excess funds to license the FDA databases.  If you have any questions regarding the databases, = please contact Leadscope at info]=[leadscope.com.<= /span>

 

 

Mike Conley

 

 

**************************************

Michael Conley

Leadscope, Inc.

1393 Dublin Road

Columbus, Ohio 43215

614-675-3732 fax

mconley]=[leadscope.com

 

------_=_NextPart_001_01C83350.B935D25F-- From owner-chemistry@ccl.net Fri Nov 30 13:21:00 2007 From: "Zhuofeng KE \(Jorphan Kerr\) jorphancore!^!yahoo.com.cn" To: CCL Subject: CCL: spin changes through the reaction Message-Id: <-35740-071130131420-20235-6b+P/mbCMAU+jTA7HBNePg-.-server.ccl.net> X-Original-From: "Zhuofeng KE \(Jorphan Kerr\)" Content-Transfer-Encoding: 8bit Content-Type: multipart/alternative; boundary="0-1390882471-1196442838=:51127" Date: Sat, 1 Dec 2007 01:13:58 +0800 (CST) MIME-Version: 1.0 Sent to CCL by: "Zhuofeng KE \(Jorphan Kerr\)" [jorphancore__yahoo.com.cn] --0-1390882471-1196442838=:51127 Content-Type: text/plain; charset=gb2312 Content-Transfer-Encoding: 8bit I think you two have arrived in agreement with each other already. Spin-inversion is a nonadiabatic process and requires an inspection for a crossing seam on the different potential energy surfaces.However, as suggest by Dongqi Wang, the excitation of A to another spin state, for example from singlet to triplet can also happen first. That is exactly what Zhu described in Eq (1) and (2). How to determine the crossing seams between the potential energy surfaces of different spin state is pretty tricky. a simple approach to approximately locate the crossing points is to analysize the potential energy surfaces with diffrent spin state. In my memory, there are two references in this topic. I hope they are helpful to you. (1)Yoshizawa, K.; Shiota, Y.; Yamabe, T. J. Chem. Phys. 1999,111, 538. Yoshizawa, K.; Kagawa, Y. J. Phys. Chem. A 2000, 104, 9347. (2)Zhang G.-B.; Li S.-H. Organometallics 2003, 22, 3820 "feng zhu zhufengcc|,|gmail.com" 写道： Thank you for you reply! I my mind, if singlet A and triplet B are the most stable states, then there must be a spin change during the reaction if the reaction can happen. So there should be three possibililities: (1) singlet A-->triplet A --> triplet B, (2) singlet A-->singlet B--> triplet B, (3) singlet A-->singlet C--> triplet C --> triplet B, Do you agree? "But as far as I know, the reaction from singlet A to triplet B is a spin-forbidden process." -- then how we study the reaction O2+C -->CO2 ? Best regards, Zhu 2007/11/29, d w : hi, zhu, you may consider the reaction in this way: 1. the reaction proceeds on the surface of spin=1 as singlet is the most stable state of A; this produces singlet B; 2. a crossing (or avoided crossing) (CI) may exist between the surfaces of singlet and triplet of B from which the singlet B will relax to triplet B. of course, in principle there is another possibility that the excitation of singlet A to triplet happens first, followed by the reaction from A to B. therefore, you need analyze your system to see if one is superior over another one, or they compete each other. But as far as I know, the reaction from singlet A to triplet B is a spin-forbidden process. good luck. best, dongqi wang Zhuofeng KE (Jorphan Kerr) -------------------------------------------------------------------- School of Chem. and Chem. Eng. Sun Yat-sen University 135 Xingangxi Road Guangzhou, 510275 P.R. China ------------------------------------------------------------------- Dept. of Chemistry CASCaM University of North Texas Denton, TX 76203-5070 ------------------------------------------------------------------- Email: jorphancore]-[yahoo.com.cn Personal blog: http://jonathankerr.spaces.live.com --------------------------------- 进入雅虎游戏嘉年华，赢取液晶显示器！ --0-1390882471-1196442838=:51127 Content-Type: text/html; charset=gb2312 Content-Transfer-Encoding: 8bit
I think you two have arrived in agreement with each other already.
Spin-inversion is a nonadiabatic process and requires an inspection for a crossing seam on the different potential energy surfaces.However, as suggest by Dongqi Wang, the excitation of A to another spin state, for example from singlet to triplet can also happen first. That is exactly what Zhu described in Eq (1) and (2). How to determine the crossing seams between the potential energy surfaces of different spin state is pretty tricky. a simple approach to
approximately locate the crossing points is to analysize the potential energy surfaces with diffrent spin state. In my memory, there are two references in this topic. I hope they are helpful to you.
(1)Yoshizawa, K.; Shiota, Y.; Yamabe, T. J. Chem. Phys. 1999,111, 538.
Yoshizawa, K.; Kagawa, Y. J. Phys. Chem. A  2000, 104, 9347.
(2)Zhang G.-B.; Li S.-H. Organometallics 2003, 22, 3820


"feng zhu zhufengcc|,|gmail.com" <owner-chemistry]-[ccl.net> 写道：
Thank you for you reply!
 
I my mind, if singlet A and triplet B are the most stable states, then there must be a spin change during the reaction if the reaction can happen.
So there should be three possibililities:
(1) singlet A-->triplet A --> triplet B,
(2) singlet A-->singlet B--> triplet B,
(3) singlet A-->singlet C--> triplet C --> triplet B,
 
Do you agree?
 
"But as far as I know, the reaction from singlet A to triplet B is a spin-forbidden process." 
-- then how we study the reaction O2+C -->CO2 ?
 
Best regards,
Zhu


 
2007/11/29, d w <wangdq2100]_[hotmail.com>:

hi, zhu,

you may consider the reaction in this way:

1. the reaction proceeds on the surface of spin=1 as singlet is the most stable state of A; this produces singlet B;
2. a crossing (or avoided crossing) (CI) may exist between the surfaces of singlet and triplet of B from which the singlet B will relax to triplet B.

of course, in principle there is another possibility that the excitation of singlet A to triplet happens first, followed by the reaction from A to B. therefore, you need analyze your system to see if one is superior over another one, or they compete each other. But as far as I know, the reaction from singlet A to triplet B is a spin-forbidden process.

good luck.

best,
dongqi wang



Zhuofeng KE  (Jorphan Kerr)  
--------------------------------------------------------------------
School of Chem. and Chem. Eng.
Sun Yat-sen University
135 Xingangxi Road
Guangzhou, 510275 P.R. China
-------------------------------------------------------------------
Dept. of Chemistry
CASCaM
University of North Texas
Denton, TX 76203-5070
-------------------------------------------------------------------
Email: jorphancore]-[yahoo.com.cn
Personal blog: http://jonathankerr.spaces.live.com

进入雅虎游戏嘉年华，赢取液晶显示器！ --0-1390882471-1196442838=:51127-- From owner-chemistry@ccl.net Fri Nov 30 15:39:01 2007 From: "Karen.Green]~[sanofi-aventis.com" To: CCL Subject: CCL: non-adiabatic processes: 2 useful refs for conceptual understanding RE: spin changes through the reaction Message-Id: <-35741-071130145731-19198-nHCzSi2HiWVWoDdFG5ufgA]-[server.ccl.net> X-Original-From: Content-class: urn:content-classes:message Content-Type: multipart/alternative; boundary="----_=_NextPart_001_01C83386.B2C87604" Date: Fri, 30 Nov 2007 12:24:59 -0700 MIME-Version: 1.0 Sent to CCL by: [Karen.Green**sanofi-aventis.com] This is a multi-part message in MIME format. ------_=_NextPart_001_01C83386.B2C87604 Content-Type: text/plain; charset="gb2312" Content-Transfer-Encoding: quoted-printable I highly recommend the following two articles which aid in obtaining a = conceptual understanding of the non-adiabatic processes involved in = reaction processes: =20 [1] Hertel, I; Rep Prog Phys 1985, 48, 375 "Angular momentum transfer and charge cloud alignment in atomic = collisions: intuitive concepts, experimental observations and = semiclassical models" =20 [2] Campbell, E; Adv Chem Phys 1988, 72, 37 "Symmetry and angular momentum in collisions with laser-excited = polarized atoms" =20 (They were very helpful for me for my chemical reaction dynamics thesis = work (J Chem Phys 2004,121(23),11760-11770 and 2000,112(4),1721-1732.)) =20 Karen M. Green --- Karen M. Green, Ph.D. Karen.Green(_)sanofi-aventis.com Research Investigator Drug Design Group Sanofi Aventis Pharmaceuticals =20 _____ =20 > From: owner-chemistry(_)ccl.net [mailto:owner-chemistry(_)ccl.net]=20 Sent: Friday, November 30, 2007 10:14 AM To: Green, Karen M. PH/US Subject: CCL: spin changes through the reaction I think you two have arrived in agreement with each other already. Spin-inversion is a nonadiabatic process and requires an inspection for = a crossing seam on the different potential energy surfaces.However, as = suggest by Dongqi Wang, the excitation of A to another spin state, for = example from singlet to triplet can also happen first. That is exactly = what Zhu described in Eq (1) and (2). How to determine the crossing = seams between the potential energy surfaces of different spin state is = pretty tricky. a simple approach to=20 approximately locate the crossing points is to analysize the potential = energy surfaces with diffrent spin state. In my memory, there are two = references in this topic. I hope they are helpful to you. (1)Yoshizawa, K.; Shiota, Y.; Yamabe, T. J. Chem. Phys. 1999,111, 538. Yoshizawa, K.; Kagawa, Y. J. Phys. Chem. A 2000, 104, 9347. (2)Zhang G.-B.; Li S.-H. Organometallics 2003, 22, 3820 "feng zhu zhufengcc|,|gmail.com" = =D0=B4=B5=C0=A3=BA =09 Thank you for you reply! =20 I my mind, if singlet A and triplet B are the most stable states, then = there must be a spin change during the reaction if the reaction can = happen. So there should be three possibililities:=20 (1) singlet A-->triplet A --> triplet B,=20 (2) singlet A-->singlet B--> triplet B,=20 (3) singlet A-->singlet C--> triplet C --> triplet B,=20 =20 Do you agree? =09 =20 "But as far as I know, the reaction from singlet A to triplet B is a = spin-forbidden process." =20 -- then how we study the reaction O2+C -->CO2 ? =20 Best regards, Zhu =09 =09 =20 2007/11/29, d w :=20 =09 hi, zhu, =09 you may consider the reaction in this way: =09 1. the reaction proceeds on the surface of spin=3D1 as singlet is the = most stable state of A; this produces singlet B;=20 2. a crossing (or avoided crossing) (CI) may exist between the = surfaces of singlet and triplet of B from which the singlet B will relax = to triplet B. =09 of course, in principle there is another possibility that the = excitation of singlet A to triplet happens first, followed by the = reaction from A to B. therefore, you need analyze your system to see if = one is superior over another one, or they compete each other. But as far = as I know, the reaction from singlet A to triplet B is a spin-forbidden = process.=20 =09 good luck. =09 best, dongqi wang =09 =09 Zhuofeng KE (Jorphan Kerr) =20 -------------------------------------------------------------------- School of Chem. and Chem. Eng. Sun Yat-sen University 135 Xingangxi Road=20 Guangzhou, 510275 P.R. China ------------------------------------------------------------------- Dept. of Chemistry CASCaM University of North Texas Denton, TX 76203-5070 ------------------------------------------------------------------- Email: jorphancore#yahoo.com.cn Personal blog: http://jonathankerr.spaces.live.com = =20 _____ =20 =BD=F8=C8=EB=D1=C5=BB=A2=D3=CE=CF=B7=BC=CE=C4=EA=BB=AA=A3=AC=D3=AE=C8=A1=D2= =BA=BE=A7=CF=D4=CA=BE=C6=F7=A3=A1 = =20 ------_=_NextPart_001_01C83386.B2C87604 Content-Type: text/html; charset="gb2312" Content-Transfer-Encoding: quoted-printable
I=20 highly recommend the following two articles which aid in obtaining = a=20 conceptual understanding of the non-adiabatic processes involved in = reaction=20 processes:
 
[1]  Hertel, I; Rep Prog Phys 1985, 48,=20 375
"Angular momentum transfer and charge cloud alignment in atomic=20 collisions:  intuitive concepts, experimental observations and=20 semiclassical models"
 
[2] Campbell, E; Adv Chem Phys 1988, 72,=20 37
"Symmetry and=20 angular momentum in collisions with laser-excited polarized=20 atoms"
 
(They = were very=20 helpful for me for my chemical reaction dynamics thesis work (J Chem = Phys=20 2004,121(23),11760-11770 and = 2000,112(4),1721-1732.))
 
Karen M. Green

---

 Karen M. Green,=20 Ph.D.

 Karen.Green(_)sanofi-aventis.com

 Research=20 Investigator

 Drug Design = Group

 Sanofi Aventis=20 Pharmaceuticals

 

From: owner-chemistry(_)ccl.net=20 [mailto:owner-chemistry(_)ccl.net]
Sent: Friday, November 30, = 2007=20 10:14 AM
To: Green, Karen M. PH/US
Subject: CCL: = spin=20 changes through the reaction

I think you two have arrived in agreement with each other=20 already.
Spin-inversion is a nonadiabatic process and requires an = inspection=20 for a crossing seam on the different potential energy surfaces.However, = as=20 suggest by Dongqi Wang, the excitation of A to another spin state, for = example=20 > from singlet to triplet can also happen first. That is exactly what Zhu=20 described in Eq (1) and (2). How to determine the crossing seams between = the=20 potential energy surfaces of different spin state is pretty tricky. a = simple=20 approach to
approximately locate the crossing points is to analysize = the=20 potential energy surfaces with diffrent spin state. In my memory, there = are two=20 references in this topic. I hope they are helpful to = you.
(1)Yoshizawa, K.;=20 Shiota, Y.; Yamabe, T. J. Chem. Phys. 1999,111, 538.
Yoshizawa, K.; = Kagawa,=20 Y. J. Phys. Chem. A  2000, 104, 9347.
(2)Zhang G.-B.; Li S.-H.=20 Organometallics 2003, 22, 3820


"feng zhu zhufengcc|,|gmail.com"=20 <owner-chemistry#ccl.net> =D0=B4=B5=C0=A3=BA
Thank you for you reply!
 
I my mind, if singlet A and triplet B are the most stable states, = then=20 there must be a spin change during the reaction if the reaction can=20 happen.
So there should be three possibililities:
(1) singlet A-->triplet A --> triplet B,
(2) singlet A-->singlet B--> triplet B,
(3) singlet A-->singlet C--> triplet C --> triplet = B,=20
 
Do you agree?
 
"But as far as I know, the reaction from singlet A to triplet B = is a=20 spin-forbidden process." 
-- then how we study the reaction O2+C -->CO2 ?
 
Best regards,
Zhu


 
2007/11/29, d w <wangdq2100]_[hotmail.com>:=20

hi,=20 zhu,

you may consider the reaction in this way:

1. the = reaction proceeds on the surface of spin=3D1 as singlet is the most = stable=20 state of A; this produces singlet B;
2. a crossing (or avoided = crossing)=20 (CI) may exist between the surfaces of singlet and triplet of B from = which=20 the singlet B will relax to triplet B.

of course, in = principle there=20 is another possibility that the excitation of singlet A to triplet = happens=20 first, followed by the reaction from A to B. therefore, you need = analyze=20 your system to see if one is superior over another one, or they = compete each=20 other. But as far as I know, the reaction from singlet A to triplet = B is a=20 spin-forbidden process.

good luck.

best,
dongqi=20 wang



Zhuofeng KE  (Jorphan=20 Kerr)  
---------------------------------------------------------------= -----
School of Chem. and Chem. Eng.
Sun Yat-sen = University
135=20 Xingangxi Road
Guangzhou, 510275 P.R. China
---------------------------------------------------------------= ----
Dept. of Chemistry
CASCaM
University of North=20 Texas
Denton, TX 76203-5070
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Email:=20 jorphancore#yahoo.com.cn
Personal blog: http://jonathankerr.spaces.live.com

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