Transcript Cossel_CombVMS_OSU2011.ppt

Frequency Comb Velocity-Modulation
Spectroscopy of HfF+
Kevin Cossel
Laura Sinclair, Tyler Coffey, Jun Ye, and Eric Cornell
OSU 2011
Acknowledgements: Huanqian Loh, Matt Grau (JILA)
John Bohn, Ed Meyer (JILA)
A. Petrov, A. Titov (Petersburg Nuc Phys Inst)
Bob Field (MIT)
Funding: NSF and the W.M. Keck Foundation
Electron Electric Dipole Moment (eEDM) search
• 3D1 metastable state of
HfF+ and ThF+ provides high
sensitivity (Hf 6s15d1)
Up to 2000 cm-1
uncertainty
E. Meyer, et. al. Phys. Rev. A 73, 062108 (2006)
• Use multiple excited states
for state preparation and
spin readout
Recently
measured with
PFI-ZEKE
• Very little spectroscopic
Barker, et al. J
data exists for either species Chem. Phys. 134
Predicted HfF+ Structure
1P
1
3P
1
3P
0
1D
2
3D
3
3D
2
3D
1
1S+
201102 (2011)
Need broadband survey
spectroscopy of molecular ions!
A. Petrov, et al. Phys. Rev. A 76, 030501 (2007)
A. Petrov, et al. Phys. Rev. A 79, 012505 (2009)
signal
Velocity-Modulation Spectroscopy
t
n
10 kHz, 1 kW
laser
Discharge produces and
modulates the ions
n
Review of VMS: Stephenson and Saykally,
Chem Rev. 105 (2005)
Ion selectivity!
Lock-in
Detector
Frequency Combs and Cavities
Frequency combs provide narrow lines over a wide spectral bandwidth.
Cavity Enhancement with a Frequency Comb:
Match Spacing of Frequency Comb Modes to Cavity’s Free Spectral Range
Cavity FSR
...
frep
Adler et al. Annu. Rev. Anal. Chem. 3 (2010)
Frequency comb + velocity modulation + cavity
3 GHz comb
Ring cavity
Finesse ~ 100
FSR ~ 120 MHz
VIPA Etalon
Vertical
dispersion
Grating
Horizontal
dispersion
10 kHz, 1 kW
(250 mA)
Artwork: B. Baxley/JILA
Lock-in detection on every comb
tooth (1500 simultaneous channels)!
Heliotis Lock-in Camera
S. Beer, P. Seitz, Research in Microelectronics
and Electronics, 2005 PhD, 2 135 (2005)
Image of comb teeth on lock-in camera
VIPA Etalon Direction
VIPA Etalon Direction
DC Intensity
~100 GHz
~3 GHz
Grating Direction
Grating Direction
Data Analysis: Fit comb teeth positions
DC Intensity [nW]
DC Intensity
100
50
0
12,150
12,200
12,250
Wavenumber [cm-1]
Data Analysis: Demodulating Each Comb Mode
Signal at 10 kHz
VIPA Etalon Direction
n
Grating Direction
Data Analysis: Scanning
28 images x1500 simultaneous channels of lock-in detection
Putting it all together: HfF+ !
fractional absorption
2
x 10
1P
-5
1
1P
1 +
1  S (0,1)
3P
1
 1S+ (2,0)
 1S+ (1,2)
1
0
-1
-2
12,000
12,100
12,200
12,300
wavenumber [cm-1]
12,400
• >500 cm-1 currently covered
• 150 cm-1 in under an hour
• 3 x 10-7 fractional sensitivity
• 3 bands (over 1000 lines) + still unidentified lines
12,500
More HfF+ !
2
x 10
-5
data
line positions for fit
1
177
HfF+
0
-1
-2
12,205
12,206
12,207 12,208 12,209
wavenumber [cm-1]
176
HfF+
178
HfF+
179
HfF+
180
HfF+
12,210
-5
fractional absorption
fractional absorption
Fit for 1P1  1S+ (0,1) band
2
x 10
1
0
-1
-2
12,208.7 12,209.2 12,209.7
wavenumber [cm-1]
Summary of 180HfF+ Fits
E(J”,J’) = T0 + (B’ – P*k’/2)J’(J’+1) - (D’ – P*kD’/2)J’2(J’+1)2 - B”J”(J”+1) + D”J”2(J”+1)2
For DJ = 0, P = -1; For DJ = ±1, P = 1
1P
1
 1S+ (0,1)
3P
1
 1S+ (2,0)
1P
1
 1S+ (1,2)
T0 [cm-1]
12217.388 (2)
12304.369 (3)
12133.977 (5)
B” [cm-1]
0.30335 (3)
0.30481 (4)*
0.30100 (50)
B’ [cm-1]
0.28115 (3)
0.28096 (4)
0.27890 (40)
D” [10-7 cm-1]
1.88 (8)
1.78 (12)
4.3 (4)
D’ [10-7 cm-1]
1.81 (8)
1.78 (11)
4.2 (4)
k‘ [10-4 cm-1]
3.69 (2)
-3.82 (1)
3.6 (5)
kD’ [10-9 cm-1]
9.7 (0.7)
-0.3 (1.0)
14 (15)
• Lambda doubling (k’) switches sign between 1P1 and 3P1
• Need lambda doubling proportional to J4 (kD’) only for 1P1
* Measured by Barker, et .al. 0.304(10)
Measured HfF+ Electronic Structure
1P
3P
1
1P
1
shifted by 1700 cm-1 from theory
1
700 cm-1
1
- 3P1 fine structure
splitting = 2100 cm-1
(theory = 2100 cm-1)
1P
3
1 & P1 oscillator
1S+ equal to ~30%
strength to
12304.369 cm-1
12133.977 cm-1
12217.388 cm-1
13002.229 cm-1
700 cm-1
1S+
1P
784.84 cm-1 consistent with Barker, et al. 785.8(10) cm-1
Theory: A. Petrov, N. Mosyagin, A. Titov, Phys. Rev. A 79 012505 (2009)
Conclusions
 Demonstrated frequency comb velocity-modulation
spectroscopy with:
• 4 x 10-8 Hz-1/2 (spectral element)-1/2 fractional absorption
sensitivity
• 150 cm-1 spectral coverage with 1500 simultaneous
measurements
• 30 MHz absolute frequency accuracy
 700 cm-1 covered so far for HfF+ (ThF+ coming soon)
 This is a very general technique which given the current
frequency comb technology could be extended across
wavelengths from the UV to the IR
 Other applications: physical chemistry (H3+, CH5+),
astrochemistry (diffuse interstellar bands)