Upload
homer-stevens
View
218
Download
0
Embed Size (px)
DESCRIPTION
Present Work High resolution (FWHM ≤ 40 MHz) experiments at ASU 50 fold improvement in resolution over previous experiments Rotational analysis of [18.6]3.5 – X(1) band Stark effect to determine dipole moments Zeeman effect to determine configurational composition of electronic states Use above to test theoretical predictions
Citation preview
STARK AND ZEEMAN EFFECT STUDY OF THE [18.6]3.5 – X(1)4.5 BAND OF URANIUM MONOFLUORIDE, UF
COLAN LINTON, ALLAN G. ADAMUniversity of New Brunswick
TIMOTHY C. STEIMLEArizona State University
Funding: DoE (TCS) NSERC (AGA)
Previous work by Antonov and Heaven JPC A117, 9684 (2013)
Experiment:
Analysis of pulsed laser excitation spectrum of [18.6]3.5-X(1)4.5 transition of UF
Ground Ω = 4.5 state is derived from U+(5f37s2 4I4.5) F- configuration
Theory:
Calculations of excited state term energies in good agreement with experiment
Calculated dipole moment of ground state μel = 1.99 Debye
Calculated composition of ground Ω=4.5 state in terms of ΛS case (a) states
Present Work• High resolution (FWHM ≤ 40 MHz) experiments at ASU• 50 fold improvement in resolution over previous experiments• Rotational analysis of [18.6]3.5 – X(1)4.5 0 - 0 band• Stark effect to determine dipole moments• Zeeman effect to determine configurational composition of electronic states• Use above to test theoretical predictions
Q branch of the [18.6]3.5 – X(1)4.5 transition of UF
Two extra lines for J′ ≥ 7.5: Upper state is perturbed
P(J′+1)Q(J′)R(J′-1)
J′=7.5
J′=8.5 J′=9.5
Stark Spectra of the P(4.5) Line of the [18.6]3.5 – X(1)4.5 transition of UF
3.43 kV/cm perpendicular
3.43 kV/cm parallel
Field free
)/5034.0()1(
DMHzJJEM Jel
Stark
Stark shift
Fit Q(4.5) and P(4.5) Stark spectra at E = 3.43, 3.14, 2.86 and 2.57 kV/cmwith laser polarized parallel and perpendicular to electric field gave
μel(X(1)4.5) = 2.01(1)D μel([18.6]3.5) = 1.88(1) D
Obs. and calc. ground state dipole moments in excellent agreement.
Reduced dipole moments μel/Re = 0.99 and 0.92 D/ÅEquivalent to nuclear charges of ~0.20e and 0.19e
Analysis of Stark effect data
Observed and Calculated Spectra of P(4.5) Line: E = 3.43 kV/cm perpendicular
Zeeman Spectra of Q(4.5 + 5.5) Transitions
Obs
CalcField
1.65 kGparallel
0 kG
)1(399.1
JJBMg Je
ZeeZeeman shift is given by
From fit to Zeeman data in R(4.5), Q(4.5), Q(5.5) at B = 1.65 kGwith laser polarized parallel and perpendicular to magnetic field
ge(X(1)4.5) = 3.28, ge([18.6]3.5)=3.26
Analysis of Zeeman effect data
Interpretation of ground state g-factor (3.28)1. In terms of molecular 2S+1ΛΣ States
Antonov and Heaven calculated composition of ground Ω=4.5 state 80.74% 4Ι4.5 + 16.50% 4Η4.5 + 2.54% 4Γ4.5+ 0.22% 4Φ4.5
(Λ=6, Σ=-1.5) (Λ=5, Σ=-0.5) (Λ=4, Σ=+0.5) (Λ=3, Σ=+1.5)
For Hund’s case (a) states, ge = (Λ + 2.002Σ) giving a calculated g-factor ge = 0.8074 x 3 + 0.1650 x 4 + 0.0254 x 5 + 0.0022 x 6 = 3.22
Calculation in very good agreement with experiment
)1(2
)1()1()1(1
aa
aae JJ
LLSSJJg
2. In terms of parent atomic states 2S+1LJa
For a Hund’s case (c) molecular Ω state derived from atomic 2S+1LJa state
Ground Ω=4.5 state of UF is derived from U+ 4I4.5 state L = 6, S= 1.5, Ja = 4.5, Ω = 4.5
ge (calc) = 3.27 ge (exp) = 3.28
Molecular ground state derived entirely from U+ (f3s2) 4I4.5 state
Excited [18.6]3.5 State (ge = 3.26):
Transition is Ω = 3.5 – 4.5.Logical choice for ΔΩ = -1 transition to predominantly 4Ι4.5 state is 4Η3.5
For 4Η3.5 ge = 5 + 2.002 x -1.5 = 2
Other possibilities giving an Ω = 3.5 state 4Γ3.5 (ge = 3): 4Φ3.5 (ge = 4): 4Δ3.5 (ge = 5)
Excited Ω = 3.5 state is possibly a mixture of predominantly 4Γ3.5 and 4Φ3.5 with possibly small contributiions from 4Η3.5, 4Δ3.5 and other states
State
Parameter X(1)4.5 [18.6]3.5
T0 (cm-1) 0 18624.5349(15)a
B0 (cm-1) 0.23247(3) 0.22754(3)a
μel (Debye) 2.01(1) 1.88(1)
ge 3.28(1) 3.26(1)
a From fit to lowest 4 levels
Molecular parameters for the X(1)4.5 and [18.6]3.5 v = 0 states of UF
Conclusions1. Field free spectra show perturbations in the upper state [18.6]3.5
2. Stark effect shows ground state dipole moment of 2.01D in excellent agreement with Antonov and Heaven calculation. Nuclear charge ~0.2e 3. Zeeman effect shows that (i) the calculated compostion of the X(1)4.5 ground state in terms of Hund’s case (a) ΛS states reproduces the observed electronic g-factor very well. (ii) The ground state arises almost entirely from the U+(5f76s2 4I4.5) F- configuration
4. The discussion on the upper state configuration is highly speculative. The g-factor suggests possible configurations and eliminates others .
5. More theoretical calculations are needed