This preview shows pages 1–4. Sign up to view the full content.
This preview has intentionally blurred sections. Sign up to view the full version.
View Full DocumentThis preview has intentionally blurred sections. Sign up to view the full version.
View Full Document
Unformatted text preview: 1 C566 Master Lecture Notes Lecture 16 From last time: Symmetric top term energies, including centrifugal distortion terms: F(J +1,K) F(J ,K) = 2B(J +1) 4D J (J +1) 3 2D JK K 2 (J +1) For 1 0, K = 0: = 2B 4D J For 2 1 K = 0, = 4B 32D J K = 1, = 4B 32D J 4D JK Dipole moments via Stark Effect Symmetric top in an electric field, E F(J, K, M) = F(E=0) + F(E) = F(J,K) + F(E) F(E) = first order term + second order term = ) 3 2 )( 1 2 ( ) 1 ( ) 1 ( ) 1 ( ) 1 2 )( 1 2 ( 2 ) 1 ( 3 2 2 2 2 3 2 2 2 2 2 2 J J J M J K J J J J M J K J gB E J J EKM M is the quantum number for the projection of total angular momentum onto the field is the permanent dipole moment Selection Rules: J = 1 K = 0 M = 0 if radiation field vector  to E = 1 if radiation field vector to E Microwave spectrometers have parallel alignment:  +  2 Diagram of the FIRST ORDER splitting of a symmetric top. Only K 0 levels will split, and the K M dependence in the 1 o term means that K = 1, M = 2 and K= 1, M= 2 levels will be degenerate, and shift the energy of the J = 2 level up. For parallel field, K = 0, M = 0 govern transitions between the degenerate pairs in the J = 1 set to the J = 2 set. Transition energies, in a parallel field: = 2B(J + 1) + ) 2 )( 1 ( 2 J J J KM h E 2 1: K = 0 = 2B(J + 1) = 4B K = 1 = 4B + 2 E/6h M = 4B + 2 E/6h for M = 1 4 B + f o r M = 4 B 2 E/6h for M = 1 If E  = 100 V/cm (mild), = 1D 3.3356410 30 Cm (mild) 2 E/6h = 1/3 (3.3310 30 Cm 100 J C1 cm 1 100cm m1 )/6.6x1034 J s ~ 15 MHz (precision ~0.01 MHz) J=1 K=0 J=2 K=0 J=2 K= 1 J=1 K= 1 4B 4B J=1 K=0 J=2 K=0 4B Apply E Apply E Degenerate pairs, with K = +1 or 1; M = 2, 1, 0, 1, 2 Degenerate pairs, with K = +1 or 1; M = 1, 0, 1 ) 1 ( J J EKM 3 Interstellar molecules Observe extraterrestrial molecules by 1. Microwave absorption of background emission (observe blanks in microwave spectrum) 2. Microwave emission A list that includes molecules discovered up to 2005 (excludes recent anion findings by Patrick Thaddeus at Harvard): http://www.cv.nrao.edu/~awootten/allmols.html Diatomic: H 2 AlF AlCl C 2 CH CH + CN CO CO + CP CSi HCl KCl NH NO NS NaCl OH PN SO SO + SiN SiO SiS CS HF SH FeO(?) Triatomics: C 3 C 2 H C 2 O C 2 S CH 2 HCN HCO HCO + HCS + HOC + H 2 O H 2 S HNC HNO MgCN MgNC N 2 H + N 2 O NaCN OCS SO2 cSiC2 CO 2 NH 2 H 3 + SiCN AlNC SiNC Four atoms: cC 3 H, lC...
View
Full
Document
This note was uploaded on 01/18/2012 for the course C 566 taught by Professor Carolinechickjarroll during the Spring '11 term at Indiana.
 Spring '11
 CarolineChickJarroll

Click to edit the document details